Circuit ISUZU KB P190 2007 Workshop Repair Manual

Engine Management – V6 – Diagnostics Page 6C1-2–65

Step Action Yes No
6 Test the HO2S heater control circuit for a high resistance, open
circuit, short to ground or short to voltage fault condition. Refer to 8A
Electrical - Body and Chassis for information on electrical fault
diagnosis.
W as any fault found and rectified? Go to Step 9 Go to Step 8
7 Replace the appropriate HO2S. Refer to 6C1-3 Engine Management
– V6 – Service Operations.
W as the repair completed? Go to Step 9 —
8 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 9 —
9 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does any of the HO2S heater control circuit DTCs fail this ignition
cycle? Go to Step 2 Go to Step 10
10 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.4 DTC P0040 or P0041
DTC Descriptor
This diagnostic procedure supports the following DTCs:
• DTC P0040 – O2 Sensor Signals Not Plausible (Bank 1, Sensor 1 & Bank 2, Sensor 1)
• DTC P0041 – O2 Sensor Signals Not Plausible (Bank 1, Sensor 2 & Bank 2, Sensor 2)
Circuit Description
The engine control relay applies positive voltage to the heater ignition voltage circuits of the HO2S. The ECM applies a
pulse width modulated (PW M) ground to the heater control circuit of the HO2S through a device within the ECM called a
driver, to control the HO2S rate of heating.
The ECM applies a voltage of approximately 450 mV between the reference signal circuit and low reference circuit of the
HO2S while the sensor temperature is less than the operating range.
Once the HO2S reaches operating temperature, the sensor varies this reference signal voltage, which constantly
fluctuates between the high voltage output and the low voltage output.
• The low voltage output is 0 – 450 mV, which occurs if the air fuel mixture is lean.
• The high voltage output is 450 – 1,000 mV, which occurs if the air fuel mixture is rich.
The ECM monitors, stores and evaluates the HO2S voltage fluctuation information to determine the level of oxygen
concentration in the exhaust.
An HO2S signal not plausible or wire connector swapped DTC sets if the ECM detects the HO2S signal voltages are
heading in the opposite direction of what was commanded.
Additional Information
• Refer to 6C1-1 Engine Management – V6 – General Information for details of the HO2S system operation.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.

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Engine Management – V6 – Diagnostics Page 6C1-2–66

• The HO2S must be tightened correctly. A loose HO2S will trigger these DTCs.
• Since fault condition in a wiring connector may trigger DTCs, always test the connectors related to this diagnostic
procedure for shorted terminals or poor wiring connection before replacing any component. Refer to 8A Electrical -
Body and Chassis for information on electrical fault diagnosis.
• To assist diagnosis, refer to 3 W iring Diagrams and Connector Charts in this Section, for the system wiring
diagram and connector charts.
Conditions for Running the DTC
Run continuously once the following conditions are met:
• The ignition voltage is 10.0 – 16.0 V.
• The engine is running.
• The O2 Sensors are in closed loop.
• The ECM is commanding the HO2Ss fuel trim.
Conditions for Setting the DTC
The ECM detects the HO2S signal voltages are heading in the opposite direction of what was commanded.
Conditions for Clearing the DTC
The HO2S signal not plausible DTCs are Type B DTCs. Refer to 1.4 Diagnostic Trouble Codes in this Section, for
action taken when Type B DTC sets and conditions for clearing Type B DTCs.
DTC P0040 and P0041 Diagnostic Table
Step Action Yes No
1 Has the Diagnostic System Check been performed?
Go to Step 2 Refer to
4.4 Diagnostic
System Check in this Section
2 1 Switch off the ignition for 30 seconds.
2 Start the engine.
3 Allow the engine to reach the normal operating temperature.
4 Increase the engine speed to 2,000 rpm for 10 seconds.
5 Using Tech 2, select the DTC display function.
Does P0040 or P0041 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 Check the HO2S 2 wiring connectors for a swapped connector fault
condition.
W as any fault found and rectified? Go to Step 5 Go to Step 4
4 Are DTCs relating to other circuits of the HO2S also set? Go to the
appropriate DTC in this Section Refer to Additional
Information in this DTC
5 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does any of the HO2S signal not plausible or wire connector swapped
DTCs fail this ignition cycle? Go to Step 2 Go to Step 6

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Engine Management – V6 – Diagnostics Page 6C1-2–67

Step Action Yes No
6 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.5 DTC P0053 or P0059
DTC Descriptor
This diagnostic procedure supports the following DTCs:
• DTC P0053 – O2 Sensor Heater Resistance Range / Performance (Bank 1, Sensor 1)
• DTC P0059 – O2 Sensor Heater Resistance Range / Performance (Bank 2, Sensor 1)
Circuit Description
The engine control relay applies positive voltage to the heater ignition voltage circuits of the HO2S. The ECM applies a
pulse width modulated (PW M) ground to the heater control circuit of the HO2S through a device within the ECM called a
driver, to control the HO2S rate of heating.
The ECM maintains the voltage between the reference signal circuit and low reference circuit of the HO2S 1 to about
450 mV by increasing or decreasing the oxygen content in the HO2S diffusion gap. To achieve this, the ECM controls
the current applied to the oxygen pumping cell in the HO2S.
• If the air / fuel mixture in the exhaust is balanced (lambda = 1), the oxygen pumping cell current is zero.
• If the exhaust gas in the HO2S 1 diffusion gap is lean, the ECM applies a positive current to the oxygen pumping
cell to discharge oxygen from the diffusion gap.
• If the exhaust gas in the HO2S 1 diffusion gap is rich, the ECM applies a negative current to the oxygen pumping
cell to draw oxygen into the diffusion gap.
The pumping current required to maintain the HO2S 1 signal circuit voltage to about 450 mV is proportional to the level
of oxygen concentration in the exhaust gas. The ECM monitors and evaluates the oxygen pumping current to determine
the level of oxygen concentration in the exhaust.
An HO2S internal heater resistance performance DTC sets if the ECM detects an internal fault condition in the ECM
HO2S heater circuit.
Conditions for Running the DTC
Run continuously once the following conditions are met:
• DTCs P0030, P0031, P0032, P0101, P0121, P012, P0123, P0131, P0132, P0133, P0221, P0222, P0223, P0336,
P0338, P2237, P2243 and P2626 ran and passed.
• The calculated exhaust temperature is greater than 400ºC.
• The engine does not misfire.
• The ignition voltage is 10.0 – 16.0 V.
• The HO2S is commanded on.
• The engine is running at speed greater than 25 rpm
Conditions for Setting the DTC
There is an internal fault condition in the ECM HO2S heater circuit.
Conditions for Clearing the DTC
The HO2S internal heater resistance performance DTCs are Type B DTCs. Refer to 1.4 Diagnostic Trouble Codes in
this Section, for action taken when Type B DTC sets and conditions for clearing Type B DTCs.

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Engine Management – V6 – Diagnostics Page 6C1-2–68

Additional Information
• Refer to 6C1-1 Engine Management – V6 – General Information for details of the HO2S system operation.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• The HO2S must be tightened correctly. A loose HO2S will trigger these DTCs.
• Since fault condition in a wiring connector may trigger DTCs, always test the connectors related to this diagnostic
procedure for shorted terminals or poor wiring connection before replacing any component. Refer to 8A Electrical -
Body and Chassis for information on electrical fault diagnosis.
• To assist diagnosis, refer to 3 W iring Diagrams and Connector Charts in this Section, for the system wiring
diagram and connector charts.
DTC P0053 and P0059 Diagnostic Table
Step Action Yes No
1 Has the Diagnostic System Check been performed?
Go to Step 2 Refer to
4.4 Diagnostic
System Check in this Section
2 1 Switch off the ignition for 30 seconds.
2 Start the engine.
3 Allow the engine to reach the normal operating temperature.
4 Increase the engine speed to 2,000 rpm for 10 seconds.
5 Using Tech 2, select the DTC display function.
Does P0053 or P0059 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 Are DTCs relating to other circuits of the HO2S also set? Go to the
appropriate DTC
Table in this Section Go to Step 4
4 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 5 —
5 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does any of the HO2S internal heater resistance performance DTCs
fail this ignition cycle? Go to Step 2 Go to Step 6
6 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.6 DTC P0101, P0102 or P0103
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0101 – Mass Air Flow Sensor Circuit Range / Performance
• DTC P0102 – Mass Air Flow Sensor Voltage Low
• DTC P0103 – Mass Air Flow Sensor Voltage High

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Engine Management – V6 – Diagnostics Page 6C1-2–69

Circuit Description
The ignition control relay applies ignition positive voltage to the mass airflow (MAF) sensor. The ECM applies 5 V
reference voltage and ground through the low reference circuit.
A heater resistor on the MAF sensor heats a micro-mechanical sensor diaphragm at a constant temperature. Two
temperature dependent resistors positioned at each side of the heater resistor measure the intake air temperature:
• The first is located at a position before the intake air passes through the heater resistor. This temperature
dependent resistor measures the temperature of the intake air before the air is heated.
• The second is located at a position after the intake air has passed through the heater resistor. This sensor
measures the temperature of the intake air after the air is heated.
The evaluation circuit on the MAF sensor converts the difference in the resistance value of these two temperature
dependent resistors into an analogue signal voltage. The ECM monitors this signal voltage through the MAF sensor
signal to calculate the engine intake air mass.
A MAF sensor circuit DTC sets if the ECM detects the actual MAF sensor signal is not within the predetermined range of
the calculated MAF sensor value.
Conditions for Running the DTC
DTC P0101
Runs continuously once the following conditions are met:
• DTCs P0121, P0122, P0123, P0221, P0222 and P0223 ran and passed.
• The engine is running.
• The ignition voltage is 10.0 – 16.0 V.
• The MAF sensor signal is -11.6 to +295 grams per second.
• The ECM detects greater than 150 crankshaft revolutions.
DTC P0102
Runs continuously once the following conditions are met:
• DTCs P0121, P0122, P0123, P0221, P0222 and P0223 ran and passed.
• The engine is running.
• The ignition voltage is 10.0 – 16.0 V.
DTC P0103
Runs continuously once the following conditions are met:
• DTCs P0121, P0122, P0123, P0221, P0222 and P0223 ran and passed.
• The engine is running at speed greater than 320 rpm
• The ignition voltage is 10.0 – 16.0 V.
Conditions for Setting the DTC
DTC P0101
The ECM detects the MAF sensor signal is not within the predetermined range of the calculated MAF value for 2
seconds.
DTC P0102
The ECM detects the MAF sensor signal is less than -11.7 grams per second.
DTC P0103
The ECM detects the MAF sensor signal is greater than 294 grams per second.

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Engine Management – V6 – Diagnostics Page 6C1-2–70

Additional Information
• The MAF sensor circuit DTCs is a Type B DTC. Refer to 1.4 Diagnostic Trouble Codes in this Section, for action
taken when a Type B DTC sets and conditions for clearing Type B DTC.
• Refer to 6C1-1 Engine Management – V6 – General Information for details of the MAF sensor operation.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• Inspect the MAF sensor for an incorrectly routed harness or if the harness is too close to the following:
− ignition coil,
− solenoids,
− relays, and
− motors.
• A low minimum air rate may cause this DTC to set during deceleration. Inspect for the following conditions:
− a plugged or a collapsed intake air duct, or a dirty air filter element,
− objects that block the MAF sensor air inlet screen, and
− sticking or dirty throttle plate or throttle bore.
• Any un-metered air that enters the engine may cause this DTC to set. Inspect for vacuum leaks in the following:
− intake manifold,
− throttle body,
− barometric pressure (BARO) sensor seal,
− EVAP canister purge valve seal,
− brake booster system,
− air induction system, and
− crankcase ventilation system.
• Since fault condition in a wiring connector may trigger DTCs, always test the connectors related to this diagnostic
procedure for shorted terminals or poor wiring connection before replacing any component. Refer to 8A Electrical -
Body and Chassis for information on electrical fault diagnosis.
• To assist diagnosis, refer to 3 W iring Diagrams and Connector Charts in this Section, for the system wiring
diagram and connector charts.
DTC P0101, P0102 or P0103 Diagnostic Table
Step Action Yes No
1 Has the Diagnostic System Check been performed?
Go to Step 2 Refer to
4.4 Diagnostic
System Check in this Section
2 1 Switch off the ignition for 30 seconds.
2 Operate the vehicle within the conditions for running the DTC.
3 Using Tech 2, select the DTC display function.
Does DTC P0101, P0102 or P0103 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC

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Engine Management – V6 – Diagnostics Page 6C1-2–71

Step Action Yes No
3 Inspect for the following fault conditions:
• engine vacuum leak,
• air leak in the intake air duct between the MAF sensor and the
throttle body,
• plugged or collapsed intake air duct,
• objects that block the MAF sensor inlet screen,
• restricted air filter element,
• restricted throttle plate or carbon build-up around the throttle
plate,
• unseated engine oil dipstick,
• loose or missing engine oil cap, and
• over filled crankcase.
W as any fault found and rectified? Go to Step 14 Go to Step 4
4 1 Disconnect the MAF sensor wiring connector.
2 Connect a test lamp between the MAF sensor ignition voltage circuit and the ECM housing.
3 Switch on the ignition with the engine not running.
Does the test lamp illuminate? Go to Step 5 Go to Step 11
5 1 Switch on the ignition with the engine not running.
2 Using a digital multimeter, measure the voltage between the MAF sensor 5 V reference circuit and the ECM housing.
Does the multimeter display 4.8 – 5.2 V? Go to Step 6 Go to Step 8
6 1 Switch off the ignition.
2 Connect a 3 A fused jumper wire between the MAF sensor 5 V reference circuit and signal circuit.
3 Switch on the ignition with the engine not running.
4 Using Tech 2, observe the MAF sensor voltage parameter.
Does Tech 2 display 4.8 – 5.2 V? Go to Step 7 Go to Step 9
7 1 Switch off the ignition.
2 Remove ECM Fuse 29 from the engine compartment fuse and relay panel assembly.
3 Using a digital multimeter, measure the resistance between the MAF sensor low reference circuit and the ECM housing.
NOTE
Install ECM Fuse 29 to the engine compartment fuse and
relay panel assembly after completing the test.
Does the multimeter display 5 Ω? Go to Step 12 Go to Step 10

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Step Action Yes No
8 Test the MAF sensor 5 V reference circuit for a high resistance, open
circuit or short to voltage fault condition. Refer to 8A Electrical - Body
and Chassis for information on electrical fault diagnosis.
NOTE
The MAF sensor shares the 5 V reference circuit with
other sensors. A fault condition in the 5 V reference circuit
will trigger DTCs on sensors that share this circuit.
W as any fault found and rectified? Go to Step 14 Go to Step 13
9 Test the MAF sensor signal circuit for a high resistance, open circuit,
short to ground or short to voltage fault condition. Refer to 8A
Electrical - Body and Chassis for information on electrical fault
diagnosis.
W as any fault found and rectified? Go to Step 14 Go to Step 13
10 Test the MAF sensor low reference circuit for a high resistance or an
open circuit fault condition. Refer to 8A Electrical - Body and Chassis
for information on electrical fault diagnosis.
W as any fault found and rectified? Go to Step 14 Go to Step 13
11 Repair the high resistance or open circuit fault condition in the MAF
sensor circuit ignition voltage. Refer to 8A Electrical - Body and
Chassis for information on electrical wiring repair procedures.
W as the repair completed? Go to Step 14 —
12 Replace the MAF sensor. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 14 —
13 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 14 —
14 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does any of the MAF Sensor Circuit DTCs fail this ignition cycle? Go to Step 2 Go to Step 15
15 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.7 DTC P0112 or P0113
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0112 – Intake Air Temperature Sensor Circuit Low Voltage
• DTC P0113 – Intake Air Temperature Sensor Circuit High Voltage
Circuit Description
The ECM applies a reference 5 V to the intake air temperature (IAT) sensor signal circuit and ground through the low
reference circuit. The IAT sensor is a variable resistor that measures the engine intake air temperature.

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Engine Management – V6 – Diagnostics Page 6C1-2–73

• Increased temperature in the intake air decreases the resistance value of the IAT sensor. This increases the IAT
sensor pull-down rate to ground. Therefore, the higher the intake air temperature, the lower the signal voltage
output of the IAT sensor.
• Decreased temperature in the intake air increases the resistance value of the IAT sensor. This reduces the IAT
sensor pull-down rate to ground. Therefore, the lower the intake air temperature, the higher the signal voltage
output of the IAT sensor.
An IAT sensor circuit DTC sets if the ECM detects the intake air temperature is outside the specified range.
Conditions for Running the DTC
Runs continuously once the following conditions are met:
• The engine is running for longer than 3.0 minutes.
• The engine is idling for longer than 10.0 seconds
Conditions for Setting the DTC
DTC P0112
The ECM detects the intake air temperature is greater than 132 °C for longer than 3.0 seconds.
DTC P0113
The ECM detects the intake air temperature is less than - 38 °C for longer than 3.0 seconds.
Conditions for Clearing the DTC
The IAT sensor DTCs are Type B DTCs. Refer to 1.4 Diagnostic Trouble Codes in this Section, for action taken when
a Type B DTC sets and conditions for clearing Type B DTC.
Additional Information
• Refer to 6C1-1 Engine Management – V6 – General Information for details of the IAT Sensor operation.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• Test the IAT sensor using the IAT Temperature vs. Resistance in 6C1-3 Engine Management – V6 – Service
Operations. If the engine has sat overnight, the IAT sensor should display within 3 °C of the ECT sensor values.
• Since fault condition in a wiring connector may trigger DTCs, always test the connectors related to this diagnostic
procedure for shorted terminals or poor wiring connection before replacing any component. Refer to 8A Electrical -
Body and Chassis for information on electrical fault diagnosis.
• To assist diagnosis, refer to 3 W iring Diagrams and Connector Charts in this Section, for the system wiring
diagram and connector charts.
Test Description
The following numbers refer to the step numbers in the diagnostic table:
3 Tests the signal circuit of the IAT sensor.
4 Measures the integrity of the IAT sensor low reference circuit. Removal of the ECM Fuse 29 enables the ECM to power down completely prior to the test procedure.
DTC P0112 or P0113 Diagnostic Table
Step Action Yes No
1 Has the Diagnostic System Check been performed?
Go to Step 2 Refer to
4.4 Diagnostic System Check in this Section

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Engine Management – V6 – Diagnostics Page 6C1-2–74

Step Action Yes No
2 1 Switch off the ignition for 30 seconds.
2 Start the engine.
3 Allow the engine to reach the normal operating temperature.
4 Using Tech 2, select the DTC display function.
Does DTC P0112 or P0113 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 1 Switch off the ignition.
2 Disconnect the IAT sensor wiring connector.
3 Switch on the ignition with the engine not running.
4 Using a digital multimeter, measure the voltage between the IAT sensor signal circuit and the ECM housing.
Does the multimeter display 4.8 – 5.2 V? Go to Step 4 Go to Step 5
4 1 Switch off the ignition.
2 Remove ECM Fuse 29 from the engine compartment fuse and relay panel assembly.
3 Using a digital multimeter, measure the resistance between the IAT sensor low reference circuit and the ECM housing.
NOTE
Install the ECM Fuse 29 to the engine compartment fuse
and relay panel assembly after completing this test.
Does the multimeter display 5 Ω? Go to Step 7 Go to Step 6
5 Test the IAT sensor signal circuit for a high resistance, open circuit,
short to ground or short to voltage fault condition. Refer to 8A
Electrical - Body and Chassis for information on electrical fault
diagnosis.
W as any fault found and rectified? Go to Step 9 Go to Step 8
6 Test the IAT sensor low reference circuit for a high resistance, open
circuit, short to ground or short to voltage fault condition. Refer to 8A
Electrical - Body and Chassis for information on electrical fault
diagnosis.
NOTE
The IAT sensor shares the low reference circuit with other
sensors. A fault condition in the low reference circuit may
trigger DTCs on sensors that share this circuit. Refer to
3 W iring Diagrams and Connector Charts in this Section,
to assist diagnosis.
W as any fault found and rectified? Go to Step 9 Go to Step 8
7 Replace the IAT sensor. Refer to 6C1-3 Engine Management – V6 –
Service Operations
W as the repair completed? Go to Step 9 —
8 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations
W as the repair completed? Go to Step 9 —

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