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How? Easy we're going to create and develop several, Independent Commercial Businesses for the interns/apprentices to work before class or after class or both, and allowed to work on weekends and paid $15.00 dollars an hour. Now the interns/apprentices are not only earning real money, but learning on the job skill social by interacting with real customers asking for their experience and help.

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Review: Assemblage of Auto Related Services to better under each individual commercial businesses. Read and Review ASSEMBLAGE OF RELATED SERVICES

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2002 Isuzu Trooper LS Trouble Codes

Power-Train Control Module (PCM)

This is the brains of the engine control system, so when the brain is not functioning correctly neither is the engine or anything else that the
microprocessor controls - which may include the charging system, transmission, various emission controls and communications with other
on-board control modules. Once a diagnosis has been made then and only then should the PCM be replaced.

Onboard Diagnostic trouble codes that typically indicate a fault with the power-train control module include:


PO601-Internal Control Module Memory Check Sum Error
PO602-Control Module Programming Error
PO603-Internal Control Module Keep Alive Memory (KAM) Error
PO604-Internal Control Module Random Access Memory (RAM) Error
PO605-Internal Control Module Read Only Memory (ROM) Error
PO606-ECM/PCM Processor
PO607-Control Module Performance
PO608-Control Module VSS Output "A"
PO609-Control Module VSS Output "B"
PO610-Control Module Vehicle Options Error

Trouble Code: PO1106
Type: Powertrain - Manufacturer Controlled DTC - Manufacturer Controlled
Description: Barometric pressure (BARO) sensor - range/performance problem
Cause: (ECM) Engine Control Modules
Main reasons for failure in Engine Control Modules

Corrosion and moisture:
Corrosion or damage due to moisture is one of the main reasons for ECM failure.
Corrosion can enter the ECM through the wiring harness and moisture can enter by a failure in the seals in the ECM itself.
This happens over a period of time (5 to 10 years) due to the ECMs exposure to the elements.

Fuel solenoid:
The electronic fuel solenoid is also a main reason for failure in the ECM. The solenoid can cause a short in the ECM due to
corrosion in the solenoid or the wire running from the solenoid to the ECM harness.
The electronic fuel solenoid is located at the top of the fuel pump. The solenoid seems to fail due to corrosion as fast as or faster than the ECM.
If your truck is running fine then you shut your engine off and it won't restart then this is a good indication that the starter has shorted out the ECM.

Injector wiring harness:
The third thing that can cause failure in the ECM is the Injector wiring harness or the sensor wiring harness. Once again corrosion or breaks
in the internal wiring in the harness can cause a short in the ECM or corrosion can enter the ECM through the wiring harness.
Again this is caused by exposure to the elements.

Grounding issues:
Another issue that can cause failure in the ECM is poor grounding. This can be the result of loose or corroded ground wires to the battery
or the frame. This is especially problematic in the Celect Plus model.

Starters:
Replacing the starter with the wrong model starter is becoming a big problem with the Celect plus ECMs. Many starter rebuilders will
bypass the override sensor in the starter. The override sensor regulates the voltage going to the ECM so when the override sensor is bypassed you will
get voltage problems in the ECM and it can generate fault codes or other problems. If you only started having problems with your ECM after installing a starter
then the starter is most likely the root of your problem.

Dead battery cells:
Dead cells in batteries can cause failure in the ECM. Many times a battery is left in the rig long after a cell has died. This affects the grounding in
the battery.

Jump start:
If the vehicle has been jump started recently and the cables were connected improperly this can cause a spike in your ECM and cause it to short out.
A bad jump can also blow out 2 amps which are located between the ECM and the firewall.

Welding and lightning:
Arc welding on the frame can blow out the ECM as well as lightning strikes. This is not very common but it does happen from time to time.

Identifying the problem:
If your check engine light is on then you should be able to read a fault code from your ECM.
The fault codes should help identify where the problem
is originating from. You can also check the voltage where the wires
come into the ECM harness with a voltmeter. The voltage should be between 9 to 12 volts for optimal usage.
Anything 6 or below and you have a problem.

Trouble Code: P0337
What does this mean?

OBD Code P0337refers to the Crankshaft position sensor also known as the crank position sensor is an electronic device used in an engine to record
the rate at which the crankshaft is spinning. This information is used by the Powertrain Control Module (PCM) or Electronic Control Module(ECM)
to control ignition and fuel injection. The sensor system consists of a rotating part, typically a disc, as well as a static part, the actual sensor.
When the engine is running, the high and low parts of the teeth cause the gap with the sensor to change. The changing gap causes the magnetic
field near the sensor to change. The change in the magnetic field cause the voltage from the sensor to change.
Symptoms
Possible sumptoms of OBD code P0337


Engine Light ON (or Service Engine Soon Warning Light) - Lack/Loss of Power - Engine Stall
Causes Possible causes of OBD code P0337 - Harness or connectors (The sensor circuit is open or shorted) - Crankshaft position sensor may be
faulty - Signal plate may be damage - Starter motor may be faulty - Starting system circuit - Dead (Weak) battery The Error code is generally activated
on detection of the following conditions: - The crankshaft position sensor (POS) signal sent to the ECM is low - The proper pulse signal from the
crankshaft position sensor (POS) is not sent to ECM Possible Solutions - Charge battery - Repair harness or connector - Replaced Crankshaft Position
Sensor.

Trouble Code: P0500
Technical Description
(VSS) Vehicle Speed Sensor Malfunction

What does that mean?
Basically this means that the vehicle’s speed as read by the Vehicle speed Sensor (VSS) in not working properly

Possible Solutions Symptoms of a P0500 DTC may include:
loss of anti-lock brakes
The "anti-lock" or "brake" warning lamps on the dash may be lit
The speedometer or odometer may not work properly (or at all)
Your vehicle's RPM limiter may be decreased
The shifting of an automatic transmission may become erratic
Other symptoms may also be present
`
Cause
A code P0500 may mean that one or more of the following has happened: The Vehicle Speed Sensor (VSS) is not reading (functioning)
properly There is a broken/frayed wire leading to the vehicle speed sensor The vehicle's PCM is not correctly configured for the actual tire size on the vehicle

Possible Solutions
The simplest thing to do is to reset the code and see if it comes back. Next, check all wiring and connectors that lead to the speed sensor.
The location of the sensor depends on your vehicle. The sensor could be on the rear axle, transmission, or perhaps the wheel hub (brake) assembly.
If the wiring and connectors are OK, then check the voltage at the speed sensor. Again, the exact procedure will depend on your make and model of vehicle.
If everything looks OK, replace the sensor.

Possible Solutions
The simplest thing to do is to reset the code and see if it comes back. Next, check all wiring and connectors that lead to the speed sensor.
The location of the sensor depends on your vehicle. The sensor could be on the rear axle, transmission, or perhaps the wheel hub (brake) assembly.
If the wiring and connectors are OK, then check the voltage at the speed sensor. Again, the exact procedure will depend on your make and model of vehicle.
If everything looks OK, replace the sensor.

Possible Cause
Faulty mass air flow sensor
Intake air leaks
Dirty mass air flow sensor
Dirty mass air filter
Mass air flow sensor harness is open or shorted
Mass air flow sensor circuit poor electrical connection

Description
The mass air flow sensor is placed in the steam of intake air. It measures the intake flow rate by measuring a part of the entire intake flow.
It consists of a hot film that is supplied with electric current from the engine control module (ECM)

The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows
around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to maintain the temperature of the hot film as air flow increases.
The ECM detects the air flow by means of this current change.

TECH NOTES:
Before replacing the mass air flow sensor, try replacing the air filter and cleaning the air flow sensor with low compress air or mass air flow sensor cleaner.
Reset code and drive vehicle. If the code comes back, it may be necessary to replaced the mass air flow sensor.

When is the code detected?
A high voltage from the sensor is sent to Engine Control Module (ECM) under light load driving condition.
A low voltage from the sensor is sent to ECM

Possible Symptoms
Engine light on (or service engine soon warning light)
Engine stall
Engine running rough
Excessive fuel consumption
Excessive smoke

Trouble Code PO101
Mass Air Flow Circuit Performance
Possible causes

  • Faulty mass air flow sensor
  • Intake air leaks
  • Dirty mass air flow sensor
  • Dirty mass air filter
  • Mass air flow sensor harness is open or shorted
  • Mass air flow sensor circuit poor electrical connection
  • When is the code detected?
  • A high voltage from the sensor is sent to Engine Control Module (ECM) under light load driving condition.
  • A low voltage from the sensor is sent to ECM
  • Possible symptoms
  • Engine Light ON (or Service Engine Soon Warning Light)
  • Engine stall
  • Engine running rough
  • Excessive fuel consumption
  • Excessive smoke
P0101 Isuzu Description
The Mass Air Flow (MAF) sensor is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire
intake flow. It consists of a hot film that is supplied with electric current from the Engine Control Module (ECM).
The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake
air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to maintain the temperature
of the hot film as air flow increases. The ECM detects the air flow by means of this current change.

Trouble Code PO102
MAP Sensor Circuit Frequency Low
Mass Air Flow Sensor Circuit Low Frequency
Possible causes Faulty mass air flow sensor Intake air leaks
Dirty mass air flow sensor Dirty mass air filter Mass air flow sensor harness is open or shorted Mass air flow sensor circuit poor electrical connection


Description
The mass air flow sensor is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow.
It consists of a hot film that is supplied with electric current from the engine control module

The temperature of the hot film
is controlled by the ECM a certain amount. The hear generated by the hot film is reduced as the intake air flows around it. The more air,
the greater the heat loss.
Therefore, the ECN must supply more electric current to maintain the temperature of the hot film as air
flow increases. The ECM detects the air flow by means
of this current change.

TECH NOTES:
Before replacing the mass air flow sensor, try replacing the air filter and cleaning the air flow sensor with low compress air or mass air flow sensor
cleaner. Reset code and drive vehicle. If the code comes back, it may be necessary to replace the mass air flow sensor.

When is the code detected?
An excessively low voltage from the sensor is sent to engine control module (ECM)
Possible symptoms
Engine light on ( or service engine soon warning light)
Engine stall
Engine running rough
Excessive fuel consumption
Excessive smoke

Trouble Code PO103 MAP Sensor Circuit Frequency High

Description
The mass air flow sensor is placed in the stream of intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is
supplied with electric current from the engine control module The temperature of the hot film is controlled by the ECM a certain amount.
The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must
supply more electric current to maintain the temperature of hte hot film as air flow increases. The ECM detects the air flow by means of this current change.

Possible causes
Faulty mass air flow sensor
Intake air leaks
Dirty mass air flow sensor
Dirty mass air filter
Mass air flow sensor harness is open or shorted
Mass air flow sensor circuit poor electrical connection

TECH NOTES:
Before replacing the mass air flow sensor, try replacing the air filter and cleaning the air flow sensor with low compress air or mass air flow
sensor cleaner. Reset code and drive vehicle. If the code comes back, it may be necessary to replace the mass air flow sensor.
An excessively high voltage from the sensor is sent to engine control module (ECM)

Possible symptoms
Engine light on ( or service engine soon warning light)
Engine stall
Engine running rough
Excessive fuel consumption
Excessive smoke

Trouble Code: PO106
MAP System Range/Performance

Description
The manifold absolute pressure sensor provides instantaneous manifold pressure information to the engine's Engine Control Module.
The data is used to calculate air density and determine the engine's air mass flow rate, which in turn determines the required fuel metering
for optimum combustion. A fuel-injected engine may alternately use a mass air flow sensor to detect the intake airflow.

When is the code detected
An excessively low or high voltage from the sensor is sent to ECM

Possible Causes
Faulty Manifold Absolute Pressure sensor
Manifold Absolute Pressure harness is open or shorted
Manifold Absolute Pressure sensor circuit poor electrical connection
Faulty engine control module

Possible symptoms
Engine light on (or service engine soon warning light)
Engine rough idle
Engine hesitation

MAP Circuit Input Low

Description
The manifold absolute pressure sensor provides instantaneous manifold pressure information to the engine's Engine Control Module.
The data is used to calculate air density and determine the engine's air mass flow rate,
which in turn determines the required fuel metering for optimum combustion. A fuel-injected engine may alternately use a mass air flow sensor to detect the intake airflow.

When is the code detected
An excessively low voltage from the sensor is sent to ECM

Possible Causes
Faulty Manifold Absolute Pressure sensor
Manifold Absolute Pressure harness is open or shorted
Manifold Absolute Pressure sensor circuit poor electrical connection
Faulty engine control module

Possible symptoms
Engine light on (or service engine soon warning light)
Engine rough idle
Engine hesitation

Trouble Code: PO108
MAP Circuit Input High

Description
The manifold absolute pressure sensor provides instantaneous manifold pressure information to the engine's Engine Control Module.
The data is used to calculate air density and determine the engine's air mass flow rate, which in turn determines the required fuel metering for optimum combustion.
A fuel-injected engine may alternately use a mass air flow sensor to detect the intake airflow.

When is the code detected
An excessively high voltage from the sensor is sent to ECM

Possible Causes
Faulty Manifold Absolute Pressure sensor
Manifold Absolute Pressure harness is open or shorted
Manifold Absolute Pressure sensor circuit poor electrical connection
Faulty engine control module

Possible symptoms
Engine light on (or service engine soon warning light)
Engine rough idle
Engine hesitation

Trouble Code: PO112
IAT Circuit Input Low


Description
The intake air temperature sensor is built into mass air flow sensor or in some vehicles mounted to the air filter duct housing.
The sensor detects intake air temperature and transmits a signal to the engine control module.
The temperature sensing unit uses a thermostat which is
sensitive to the change in temperature.
Electrical resistance of the thermostat decreases in response to the temperature rise. The intake air temperature signal is used as an
input for various systems in the vehicle

When is the code detected
An excessively low voltage from the sensor is sent to ECM

Possible Causes
Faulty intake air temperature Sensor
Dirty air filter
Intake air temperature sensor harness is open or shorted
Intake air temperature sensor circuit poor electrical connection

Possible symptoms
Engine light on (or service engine soon warning light)

Trouble Code: PO113
IAT Circuit Input High


Description
The intake air temperature sensor is built into mass air flow sensor or in some vehicles mounted to the air filter duct housing.
The sensor detects intake air temperature nd transmits a signal to the engine control module. The temperature sensing unit uses a
thermostat which is sensitive to the change in temperature. Electrical resistance of the thermostat decreases in response to the
temperature rise. The intake air temperature signal is used as in input for various systems in the vehicle.

When is the code detected
An excessively high voltage from the sensor is sent to ECM

Possible Causes:
Faulty intake air temperature sensor
Dirty air filter
Intake air temperature sensor harness is open or shorted
Intake air temperature sensor circuit poor electrical connection

Possible symptoms
Engine light on ( or service engine soon warning light)

Trouble Code: PO116
ECT Circuit Range/Performance

Description
The Engine Coolant Temperature (ECT) sensor is used to detect the engine coolant temperature.
The sensor modifies a voltage signal from the Engine Control Module (ECM). The modified signal returns to the ECM as
the engine coolant temperature input. The sensor uses a thermostat which is sensitive to the change in temperature.
The electrical resistance of the thermostat decreases as temperature increases.

Possible Causes:
Low engine coolant level
Faulty Engine Coolant Temperature (ECT) sensor
Faulty engine coolant thermostat
Engine Coolant Temperature (ECT) sensor harness is open or shorted
Engine Coolant Temperature (ECT) sensor circuit poor electrical connection

Possible Symptoms
Engine Light ON (or Service Engine Soon Warning Light)

Trouble Code: PO117
ECT Circuit Input Low

Description
The Engine Coolant Temperature (ECT) sensor is used to detect the engine coolant temperature.
The sensor modifies a voltage signal from the Engine Control Module (ECM). The modified signal returns to the ECM as the engine
coolant temperature input. The sensor uses a thermostat which is sensitive to the change in temperature.
The electrical resistance of the thermostat decreases as temperature increases.

When is the code detected?
An excessively low voltage from the sensor is sent to ECM.

Possible Causes:
Low engine coolant level
Faulty Engine Coolant Temperature (ECT) sensor
Faulty engine coolant thermostat
Engine Coolant Temperature (ECT) sensor harness is open or shorted
Engine Coolant Temperature (ECT) sensor circuit poor electrical connection

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)

Trouble Code: PO118
ECT Circuit Input High


Description:
The Engine Coolant Temperature (ECT) sensor is used to detect the engine coolant temperature. The sensor modifies a voltage
signal from the Engine Control Module (ECM). The modified signal returns to the ECM as the engine coolant temperature input.
The sensor uses a thermostat which is sensitive to the change in temperature. The electrical resistance of the thermostat decreases
as temperature increases.

When is the code detected?
An excessively high voltage from the sensor is sent to ECM.

Possible Causes:
Low engine coolant level
Faulty Engine Coolant Temperature (ECT) sensor
Faulty engine coolant thermostat
Engine Coolant Temperature (ECT) sensor harness is open or shorted
Engine Coolant Temperature (ECT) sensor electrical circuit poor connection

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)

rouble Code: PO121
TP Sensor System Performance

Description: which transforms the throttle position into output voltage, and emits the voltage signal to the Engine Control Module (ECM).
In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the ECM.
Idle position of the throttle valve is determined by the ECM receiving the signal from the throttle position sensor.
This sensor controls engine operation such as fuel cut. On the other hand, the Wide open and closed throttle position switch,
which is built into the throttle position sensor unit, is not used for engine control. When is the code detected?
Sensor input voltage does not fall within a valid range based on engine speed and load

Possible Cause:
Faulty throttle position sensor
Throttle position sensor harness is open or shorted
Throttle position sensor circuit poor electrical connection
Faulty Engine Control Module (ECM)

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)

Trouble Code: PO122 Description:
The Throttle Pedal Position (TPP) responds to the accelerator pedal movement. This sensor is a kind of potentiometer
which transforms the throttle position into output voltage, and emits the voltage signal to the Engine Control Module (ECM).
In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the ECM.
Idle position of the throttle valve is determined by the ECM receiving the signal from the throttle position sensor.
This sensor controls engine operation such as fuel cut. On the other hand, the Wide open and closed throttle position switch,
which is built into the throttle position sensor unit, is not used for engine control.

When it the code detected?
An excessively low voltage from the Throttle Position Sensor (TPS) is sent to Engine Control Module (ECM).

Possible Cause:
Faulty throttle position sensor.
Throttle position sensor harness is open or shorted
Throttle position sensor circuit poor electrical connection

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)

Trouble Code: PO123
TP Sensor Circuit Input High

Description:
The Manifold Absolute Pressure (MAP) sensor provides instantaneous manifold pressure information to the
engine's Engine Control Module (ECM). The data is used to calculate air density and determine the engine's air mass flow rate,
which in turn determines the required fuel metering for optimum combustion. A fuel-injected engine may alternately use a
Mass Air Flow (MAF) sensor to detect the intake airflow.

When is the code detected?
An excessively high voltage from the sensor is sent to ECM

Possible Cause:
Faulty Manifold Absolute Pressure sensor
Manifold Absolute Pressure harness is open or shorted
Manifold Absolute Pressure sensor circuit poor electrical connection
Faulty Engine Control Module (ECM)

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)
Engine rough idle
Engine hesitation

Trouble Code: PO126
Insufficient Coolant Temperature for Stable Operation

Description:
The Engine Coolant Temperature (ECT) sensor is used to detect the engine coolant temperature. The sensor modifies a voltage
signal from the Engine Control Module (ECM). The modified signal returns to the ECM as the engine coolant temperature input.
The sensor uses a thermostat which is sensitive to the change in temperature. The electrical resistance of the thermostat decreases
as temperature increases.

When is the code detected?
The voltage sent to Engine Control Module (ECM) from the sensor is not practical, even when some time has passed after starting the engine.
Possible Causes:
Low engine coolant level
Leaking or stuck open thermostat
Faulty Engine Coolant Temperature (ECT) sensor
Engine Coolant Temperature (ECT) sensor harness is open or shorted
Engine Coolant Temperature (ECT) sensor electrical circuit poor connection

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)

Trouble Code: PO128
Engine Coolant Temperature Below Thermostat Regulating Temperature

Description:
Indicates that the thermostat monitor has not achieved the required engine operating temperature within a specified amount
of time after starting the engine.

When is the code detected?
The engine coolant temperature does not reach to specified temperature even though the engine has run long enough.

Possible Causes:
Leaking or stuck open thermostat
Low engine coolant level
Insufficient warm up time
Faulty engine coolant temperature sensor
Engine coolant temperature sensor harness is open or shorted
Engine coolant temperature sensor circuit poor electrical connection

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)

Trouble Code: PO130
HO2S Circuit Sensor 1


Description:
The front heated oxygen sensor (or O2 sensor 1) is placed into the exhaust manifold. It detects the amount of oxygen
in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia.
The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions.
The heated oxygen sensor 1 signal is sent to the Engine Control Module (ECM). The ECM adjusts the injection pulse duration to achieve the ideal
air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.

When is the code detected?
The response of the voltage signal from the sensor takes more than the specified time.

Possible Causes:
Faulty Front Heated Oxygen Sensor Bank 1
Front Heated Oxygen Sensor Bank 1 harness is open or shorted
Front Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)
High Fuel Consumption
Excessive Smoke from Exhaust

Trouble Code: PO132
HO2S Circuit High Voltage Sensor 1
Description:
The front heated oxygen sensor (or O2 sensor 1) is placed into the exhaust manifold. It detects the amount of oxygen
in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia.
The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions.
The heated oxygen sensor 1 signal is sent to the Engine Control Module (ECM). The ECM adjusts the injection pulse duration to achieve
the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.

When is the code detected?
An excessively high voltage from the sensor is sent to Engine Control Module (ECM).

Possible Causes:
Faulty Front Heated Oxygen Sensor Bank 1
Front Heated Oxygen Sensor Bank 1 harness is open or shorted
Front Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)
High Fuel Consumption
Excessive Smoke from Exhaust

Trouble Code: PO133
HO2S Slow Response Sensor 1
Description:
The front heated oxygen sensor (or O2 sensor 1) is placed into the exhaust manifold. It detects the amount of oxygen
in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia.
The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions.
The heated oxygen sensor 1 signal is sent to the Engine Control Module (ECM). The ECM adjusts the injection pulse duration
to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.

When is the code detected?
The response of the voltage signal from the sensor takes more than the specified time.

Possible Causes:
Faulty Front Heated Oxygen Sensor Bank 1
Front Heated Oxygen Sensor Bank 1 harness is open or shorted
Front Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light
High Fuel Consumption
Excessive Smoke from Exhaust

Trouble Code: PO134
HO2S Circuit Insufficient Activity Sensor 1
Description:
The front heated oxygen sensor (or O2 sensor 1) is placed into the exhaust manifold. It detects the amount of oxygen
in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia.
The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions.
The heated oxygen sensor 1 signal is sent to the Engine Control Module (ECM). The ECM adjusts the injection pulse duration
to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.

When is the code detected?
The voltage from the sensor is constantly approx. 0.3V.
Possible Causes:
Faulty Front Heated Oxygen Sensor Bank 1
Front Heated Oxygen Sensor Bank 1 harness is open or shorted
Front Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty

Exhaust gas leaks
Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)
High Fuel Consumption
Excessive Smoke from Exhaust

Trouble Code: PO135
HO2S Heater Performance Sensor 1
Description:
Oxygen Sensor (02S) or Heated Oxygen Sensor (H02S) need to reach a minimum operating temperature of 750 degrees F
to produce an accurate voltage signal. The faster the heated oxygen sensor reaches that temperature temperature the faster
the sensor will start sending an accurate signal to the Engine Control Module (ECM)

In order to achieve the require temperature, a heater element is included inside the heated oxygen sensor. The ECM controls
the heated oxygen sensor heater element based on signals from the engine coolant temperature and engine load. The ECM controls
the heater element circuit by allowing current flow to ground.

The ECM monitors the voltage signal received through the heater element circuit and determines the state of the circuit by comparing
the voltage detected with the factory specifications.



When is the code detected?
Current amperage in the front heated oxygen sensor heater circuit is out of the normal range. (An improper voltage drop signal
is sent to ECM through the front heated oxygen sensor heat

Possible Causes:
Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1
Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit fuse
Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit open shorted to ground
Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit poor electrical connection
Faulty Engine Control Module (ECM)

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)
Possible higher than usual fuel Consumption

Trouble Code: PO136
HO2S Circuit Sensor 2
Description:
The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank.
For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio.
The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts
the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response
to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when
the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when
the HO2S voltage is above 0.45 V.

When is the code detected?
It takes more time for the sensor to respond between rich and lean than the specified time.
Possible Cause:
Faulty Rear Heated Oxygen Sensor Bank 1
Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)
High Fuel Consumption
Excessive Smoke from Exhaust

TECH NOTES:
Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem


Trouble Code: PO138
Description:
The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after three way catalyst (manifold), monitors the oxygen level
in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near
the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio.
The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric.
The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas
increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust
gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.

When is the code detected?
The P0138 code is set when the Engine Control Module (ECM) detects that the rear O2 sensor signal voltage remains excessively high for
an extended period of time.

Possible Causes:
Faulty Rear Heated Oxygen Sensor Bank 1
Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Intake air leaks
Exhaust gas leaks
Inappropriate fuel pressure
Faulty fuel injectors

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)
High Fuel Consumption
Excessive Smoke from Exhaust

TECH NOTES:
Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.


HO2S Circuit Low Voltage Sensor 2
Trouble Code: PO140
HO2S Circuit High Voltage Sensor 2


Description:
The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank.
For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio.
The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the
fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to
oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the
HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the
HO2S voltage is above 0.45 V.

When is the code detected?
The P0140 code is set when the voltage signal sent from the sensor to the Engine Control Module is constant.
Possible Causes:
Faulty Rear Heated Oxygen Sensor Bank 1
Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks
Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)
High Fuel Consumption
Excessive Smoke from Exhaust

TECH NOTES:
Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.


Trouble Code: PO141
HO2S Heater Performance Sensor 2
Description:
Oxygen Sensors (O2S) or Heated Oxygen Sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to
produce an accurate voltage signal. The faster the heated oxygen sensor reaches that temperature the faster the sensor will start sending
an accurate signal to the Engine Control Module (ECM). In order to achieve the require temperature, a heater element is included inside
the heated oxygen sensor. The ECM controls the heated oxygen sensor heater element based on signals from the engine coolant temperature
and engine load. The ECM controls the heater element circuit by allowing current flow to ground. The ECM monitors the voltage signal received
through the heater element circuit and determines the state of the circuit by comparing the voltage detected with the factory specifications.

When is the code detected?
Current amperage in the rear heated oxygen sensor heater circuit is out of the normal range.
Possible Causes:
Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2
Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit fuse
Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit open shorted to ground
Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit poor electrical connection
Faulty Engine Control Module (ECM)

Possible Symptoms:
Engine Light ON (or Service Engine Soon Warning Light)
Possible higher than usual fuel Consumption

TECH NOTES:
The code means that there is a problem with the heater element circuit of the heated oxygen sensor. The control module
monitors how long it take the sensor to warm up and start sending an adequate signal. The code is triggered when the sensor
is taking too long to warm up. Water getting inside the heated oxygen sensor connector can caused the heated oxygen sensor fuse to blow.
Before replacing the sensor, check for the condition of the heated oxygen sensor fuse and connectors. If the sensor and connector are OK,
replacing the O2 Sensor 1 usually takes care of the problem


Trouble Code: PO142
02 Sensor Circuit Malfunction (Bank I Sensor 3)

Description:
The oxygen sensors are critical to the engine running properly. It basically informs the PCM (Powertrain Control Module) of oxygen
content of the exhaust. The PCM then uses this information to regulate fuel injector pulse. Inaccurate or faulty O2 sensors can cause the
PCM to add or take away fuel based on the faulty O2 sensor voltage which can cause a host of problems. A P0142 code refers to the
Bank 1,3 O2 sensor or the 3rd downstream (post-cat) O2 sensor on Bank 1. It is a four wire sensor. The PCM supplies a ground circuit and
a reference voltage circuit of about 0.5volts . Also for the O2 sensor heater element there is a battery voltage supply wire and another ground
circuit for that. The O2 sensor heater allows the O2 sensor to warm up faster, thus achieving closed loop in less time than it would normally
take for the exhaust to warm the sensor up to operating temperature. The O2 sensor varies the supplied reference voltage based on oxygen
content in the exhaust. It is capable of varying from about 0.1 to 0.9 volts, 0.1v indicating lean exhaust and 0.9v indicating rich exhaust.
This P0142 code indicates that the Bank 1,3 O2 sensor is stuck low for too long or isn't active at all.

Cause:
Potential causes of a P0142 code include: Bad O2 sensor Signal shorted to voltage Wiring problems due to contact with exhaust
components Holes in exhaust near O2 sensor

Possible Symptoms:
Often post-cat O2 sensor problems present few symptoms since they are inputs to the PCM to monitor catalytic converter quality and don't
directly control fuel. sometimes no symptoms are noticeable. However the following may be possible on some vehicles:
MIL (Malfunction Indicator Lamp) illumination
Decrease in MPG
Increase in tailpipe emissions

Possible Solutions:
If you have access to a scan tool, check the signal voltage for the Bank 1,3 oxygen sensor with the engine at normal operating temperature.
Is it stuck low currently? If so, increase RPM for a few seconds and see if it affects the reading. If it begins working with increased RPM,
check for holes in the exhaust near the O2 sensor that may cause a false lean. If the exhaust pipe is intact, the sensor is sluggish, replace it.
If the Bank 1,3 O2 sensor voltage reading remains low with increased RPM, unplug it and then observe the reading. It should have increased
to about 0.5 volts or thereabouts. If it did, check for water intrusion or other connector problems. If none are found, replace the shorted O2 sensor.
If the voltage reading is still stuck low after unplugging the sensor, then suspect a wiring problem. Using a voltmeter, with the O2 sensor unplugged,
check for voltage on the signal circuit at the O2 sensor connector (PCM side). It can vary with model, but should be about 0.5 volts and not above 1 volt.
If the voltage reading is too high, repair short to voltage on signal circuit. If the signal voltage checks out, suspect the PCM.

Trouble Code: PO143
HO2S Sensor Circuit Low Voltage (Bank 1 Sensor3)

What does that mean?
The Catalytic Converter is used to help control emissions. The PCM (Powertrain Control Module) uses the signal from the oxygen sensor to the
rear of the catalyst to monitor the catalyst's efficiency.

This is the bank 1,3 sensor. It's a four wire sensor being supplied a 0.5 volt reference voltage as well as a power and ground circuit for the
o2 sensor heater element. There is also a signal wire from the oxygen sensor to the PCM that can vary between about 0.1 volts to about 0.9 volts
according to oxygen content of the exhaust. A properly working post-cat sensor will exhibit small changes at a slower rate than front o2 sensors.
To over simplify: a post-cat sensor's main job is to monitor catalyst efficiency, not control fuel management (although they can have a measure
of influence over the front o2 sensor's operation). If the PCM determines that the post-cat o2 sensor signal voltage is below a certain threshold for
too long, P0143 will set. PCM detected the HO2S signal was less than 156 mv for 28 seconds.

Symptoms:
Usually rear o2 sensor problems won't cause drivability issues since they are an input that measures catalyst efficiency (unlike front o2 sensors).
However if you have other codes present, like lean codes or pre-o2 sensor codes, then they may cause drivability problems as well as P0143.
The following symptoms may be present:
  • MIL (Malfunction Indicator Lamp) illumination
  • Engine performance issues
  • Engine running rough
  • Engine running rich
  • Poor idle

Cause:
An engine that is running lean could set this code, however there will likely be other codes present.
  • Air leaks in exhaust in front of:
  • O2 sensor giving false reading
  • O2 sensor connector damaged
  • O2 sensor signal circuit is shorted to ground
  • O2 sensor ground circuit is open
  • O2 sensor has failed (it may be contaminated with fuel or coolant)
  • PCM has failed

Solutions:
With KOER (Key on engine running) use a scan tool or a voltmeter check the o2 sensor signal voltage with engine warm. You may have
to increase the RPM to a fast idle to check the voltage of the bank 1,3 sensor. If it's voltage is stuck low (less than a half a volt) and you don't
have any other o2 sensor codes present in the PCM, then it's a good bet that the sensor is bad. If the voltage isn't stuck low and the o2 sensor
seems to be operating fine, it's likely sticking low intermittently. This often turns out to be the sensor.

Having said that, if you're interested in knowing for sure what the problem is then perform the following: 1. Turn off the engine and unplug
the 1,3 o2 sensor connector. Make sure that there is battery voltage present and ground present for the o2 sensor heater. If there isn't then
diagnose that first then retest. If that checks out then, using a jumper wire, supply a chassis ground to the o2 sensor connector (PCM side)
ground circuit. Now observe the scan tool bank 1,3 o2 sensor reading. If it is now at about a half a volt then replace the o2 sensor. If, after
supplying a ground to the unplugged PCM side of the o2 sensor connector, the voltage reading doesn't change then check the harness for short
to ground.

Check for harness making contact with exhaust components. Check pins for damage, and for moisture. Repair as necessary. If you can find no
harness problems, then the PCM may be bad.


Trouble Code: PO144
HO2S Sensor Circuit High Voltage (Bank I Sensor 3)
What Does that Mean?
The catalytic converter is used to lower harmful emissions. To ensure proper operation, there is an O2 sensor located behind the catalyst
that monitors the oxygen content of the exhaust after the cat. The PCM (Powertrain Control Module) then compares the post-cat reading to
the pre-cat readings to determine if the catalyst is working properly.

A P0144 refers to a fault at the post-cat o2 sensor, indicating that the signal voltage is too high. The o2 sensor is a four wire sensor.
Two wires are dedicated to the heating element and two wires are dedicated to the sensor. The heating element should have battery voltage
on one wire with key on engine off and ground should be present on the other. The PCM supplies a reference voltage to the o2 sensor which the
sensor varies according to oxygen content in the exhaust. It is capable of varying between approximately 0.1 and 0.9 volts. This variance in the
voltage is monitored by the PCM. The PCM also supplies a ground to the sensor. P0144 means that the voltage was too high on the signal circuit.

Symptoms:
  • MIL (Malfunction Indicator Lamp) on:
  • Engine loses power and misses intermittently
  • May exhibit loss of fuel efficiency
  • Cause:
  • Bad o2 sensor (Bank 1 Sensor 3)
  • Wiring in contact with exhaust components
  • Engine running rich (If other codes are present)
  • Holes in exhaust near Bank 1 Sensor 3
  • Short to voltage on signal circuit

Bad PCM
Possible Solutions: Start the engine and observe the Bank 1 Sensor 3 (a.k.a. 1/3) o2 sensor voltage. You may need to raise the idle up until the
o2 sensor starts switching.
If it is stuck high, or close to 1 volt and the voltage doesn't vary, then check for a good ground on both the heater element and the sensor.
Also check that the heater element is being supplied good battery voltage. No heater operation can cause a sluggish sensor.

If the grounds are good and the battery voltage is present, then jumper the sensor's signal wire to the sensor's ground wire.
Now the scan tool should read low or near zero volts. If it does, the wiring is good. Replace the bank 1/3 o2 sensor. If jumping the signal
wire to the ground doesn't lower the voltage, and then check the o2 sensor wiring harness. Make sure there is no contact with hot exhaust
components. Ensure good wiring harness connections. If the wiring checks out, then re-perform the previous wiring harness checks at the
PCM connector.

If now the 1/3 o2 sensor reading drops, then there is a wiring problem that isn't visible. Open the harness and visually inspect the wiring for
problems. But if the result is the same, then the PCM may be bad.

Trouble Code: PO146
H02S Sensor Circuit No Activity Detected (Bank I Sensor 3)

What does that mean?
The catalytic converter is used to control emissions. The o2 sensor on Bank 1, position 3 is aft of the converter and monitors the catalyst efficiency.
The PCM (Powertrain Control Module) does this by comparing the post-cat o2 sensor to the pre-cat o2 sensors.

The o2 sensor is a four wire sensor. The PCM supplies a reference to the sensor of about half a volt and also supplies a sensor ground and 12 volts
for the heater element. The fourth wire is a ground for the heater element (the heater in the sensor helps the sensor to warm up faster which allows
the engine to reach closed loop sooner).

The sensor varies the supplied reference voltage based on oxygen content of the exhaust. Oxygen sensors are capable of varying between
0.1 volts to 0.9 volts. Lean exhaust produces low voltage and causes the supplied 0.45 volts to drop. Rich exhaust produces high voltage and causes
the supplied 0.45 voltage to increase. Precatalyst o2 sensors switch between low and high voltage rapidly. However a post-cat o2 sensor may switch
much slower & not vary as much (this is normal). If the sensor doesn't respond as it should or there are too few switches in a given time period,
P0146 may set.

Symptoms:
  • MIL (Malfunction Indicator Lamp) on:
  • May idle or drive poorly
  • Fuel economy may decrease
  • Causes:
  • Bad Bank 1, position 3, o2 sensor
  • Wiring problem, melted harness, broken connectors, etc.
  • Bad PCM

Possible Solutions:
1. Start the engine and allow it to reach operating temperature. Using a scan tool, observe the Bank 1 position 3 o2 sensor. If it isn't moving
between 0.1 and 0.9 volts, increase the engine RPM to a fast idle and then recheck the sensor voltage reading. If it starts switching now, the sensor
may be sluggish and/or intermittently going "dormant". Replacing the sensor at this point would be a good idea.

Visually check the o2 sensor for contaminates, etc. If you suspect it's contaminated with coolant or oil, replace it.

a. But, if it still isn't responding after increasing engine RPM, turn off the engine and unplug the 1/3 o2 sensor. With KOEO (key on engine off) check
that there is battery voltage and ground to the o2 sensor heater element. If the heater element has no battery voltage it can cause the o2 sensor to
go "dormant" and not switch properly which can cause a P0146. So, diagnose that problem first, there will usually be other codes present).

b. If there is power and ground to the heater element check that the sensor ground is present.

If it is, connect a jumper wire between the sensor ground
and signal wire. Now the 1/3 o2 sensor reading should be low. If so, replace the Bank 1 position 3 o2 sensor.

c. If, after connecting the jumper wire, the o2 sensor reading still remains "stuck", check for wiring problems, harness contacting exhaust components,
or broken connectors. Repair as necessary. Then recheck.

d. If you can find no wiring problems and the o2 sensor reading on the scan tool doesn't change after installing the jumper wire, recheck at the PCM
connector. If it still shows no change, the PCM may be at fault.