2007 ISUZU KB P190 ignition

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

BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–72

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.

BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007

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 —

BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–75

Step Action Yes No
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 IAT sensor 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.
7.8 DTC P0116, P0117, P0118, P0125 or
P1258
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0116 – Engine Coolant Temperature Sensor Circuit Range / Performance
• DTC P0117 – Engine Coolant Temperature Sensor Circuit Low Voltage
• DTC P0118 – Engine Coolant Temperature Sensor Circuit High Voltage
• DTC P0125 – Insufficient Engine Coolant Temperature For Closed Loop Fuel Control
• DTC P1258 – Engine Coolant Over Temperature - Protection Mode Active
Circuit Description
The ECM applies a reference 5 V to the engine coolant temperature (ECT) sensor signal circuit and ground through the
low reference circuit. The ECT sensor is a variable resistor that measures the temperature of the engine coolant.
• Increased temperature in the engine coolant decreases the resistance value of the ECT sensor. This increases the
ECT sensor pull-down rate to ground. Therefore, the higher the engine coolant, the lower the signal voltage output
of the ECT sensor.
• Decreased temperature in the engine coolant increases the resistance value of the ECT sensor. This reduces the
ECT sensor pull-down rate to ground. Therefore, the lower the engine coolant temperature, the higher the signal
voltage output of the ECT sensor.
An ECT sensor DTC sets if the ECM detects the engine coolant temperature is outside the predetermined range.
Conditions for Running the DTC
DTC P0116
Runs continuously when the engine is running.
DTC P0117, P0118 and P1258
Runs continuously when the ignition is switched on.
DTC P00125
Runs continuously once the following conditions are met:
• DTCs P0112, P0113, P0117 or P0118 are not set.
• The engine is running.

BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–77

Step Action Yes No
2 Test the engine cooling system for correct operation. Refer to 6B1
Engine Cooling – V6.
W as any fault found and rectified? Go to Step 10 Go to Step 3
3 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 P0116, P0117, P0118, P0125 or P1258 fail this ignition
cycle? Go to Step 4 Refer to Additional
Information in this DTC
4 1 Switch off the ignition.
2 Disconnect the ECT sensor wiring connector.
3 Switch on the ignition with the engine not running.
4 Using a digital multimeter, measure the voltage between the ECT sensor signal circuit and the ECM housing.
Does the multimeter display 4.8 – 5.2 V? Go to Step 5 Go to Step 6
5 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 ECT 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 8 Go to Step 7
6 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 10 Go to Step 9
7 Test the ECT 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 ECT 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 10 Go to Step 9
8 Replace the ECT sensor. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 10 —
9 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 10 —

BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–78

Step Action Yes No
10 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 ECT sensor DTCs fail this ignition cycle? Go to Step 2 Go to Step 11
11 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.
7.9 DTC P0121, P0122, P0123, P0221,
P0222,or P0223
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0121 – Throttle Position Sensor 1 Circuit Range / Performance
• DTC P0122 – Throttle Position Sensor 1 Circuit Low Voltage
• DTC P0123 – Throttle Position Sensor 1 Circuit High Voltage
• DTC P0221 – Throttle Position Sensor 2 Circuit Range / Performance
• DTC P0222 – Throttle Position Sensor 2 Circuit Low Voltage
• DTC P0223 – Throttle Position Sensor 2 Circuit High Voltage
Circuit Description
The ECM applies 5 V to the throttle position (TP) sensor 1 through the 5 V reference circuit and the ground through the
low reference circuit. TP sensor 1 and TP sensor 2 share common 5 V reference circuit and low reference circuit.
The TP sensor 1 and TP sensor 2 have individual signal circuits with opposite functionality. These signal circuits provide
the ECM with a signal voltage that is proportional to the throttle plate movement.
• The TP sensor 1 signal voltage is less than 1 V when the throttle plate is in closed position, which increases to
greater than 4 V when the throttle plate is moved to wide-open throttle.
• The TP sensor 2 signal voltage is greater than 4 V when the throttle plate is in closed position, which decreases to
less than 1 V when the throttle plate is moved to wide-open throttle.
The ECM monitors and compares the TP sensor 1 signal voltage to the TP sensor signal voltage 2. In addition, the ECM
compares the TP sensor signal to the MAF sensor signal to determine a calculated TP sensor signal.
A TP sensor DTC sets if the ECM detects a fault condition in the TP sensor signal output.
Conditions for Running the DTC
DTC P0121 runs continuously once the following conditions are met:
• The ignition voltage is greater than 7 V.
• The TP sensor 1 signal voltage is 0.17 – 4.6 V.
DTC P0122, P0123, P0222 and P0223 runs continuously once the following conditions are met:
• The ignition voltage is greater than 7 V.
• The ignition is switched on.
DTC P0221 runs continuously once the following conditions are met:
• The battery voltage is greater than 7 V.

BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–79

• The TP sensor 2 signal voltage is 0.15 – 4.8 V.
DTC P0222 runs continuously once the following conditions are met:
• The battery voltage is greater than 7 V.
• The ignition is switched on.
Conditions for Setting the DTC
DTC P0121
The following conditions exist:
• The TP sensor 1 signal voltage and the TP sensor 2 signal voltage have a difference of greater than 9 percent.
• The TP sensor signal voltage has a difference of greater than 9 percent from the calculated TP sensor signal
voltage.
DTC P0122
The ECM detects the TP sensor 1 signal voltage is less than 0.18 volt.
DTC P0123
The ECM detects the TP sensor 1 signal voltage is greater than 4.6 V.
DTC P0221
The following conditions exist:
• The TP sensor 2 signal voltage and the TP sensor 1 signal voltage have a difference of greater than 9 percent.
• The TP sensor 2 signal voltage has a difference of greater than 9 percent from the calculated TP sensor signal
voltage.
DTC P0222
The ECM detects the TP sensor 2 signal voltage is less than 0.16 volt.
DTC P0223
The ECM detects the TP sensor 2 signal voltage is greater than 4.8 V.
Conditions for Clearing the DTC
DTCs P0121, P0122, P0123, P0221, P0222 are P0223 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 DTCs.
Additional Information
• Refer to 6C1-1 Engine Management – V6 – General Information for details of the TP sensor operation.
• The ECM defaults to a reduced power mode if there is a fault condition in the TP sensor circuits for the entire
ignition cycle, even if the fault condition is corrected.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• The TP sensors share a common 5 V reference circuit, test for a fault condition in the 5 V reference circuit if both
DTCs P0122 and P0222 are set.
• 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.

BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–80

Test Description
The following number refers to the step number in the diagnostic table:
6 Measures the integrity of the TP sensor low reference circuit. Removal of the ECM Fuse 29 enables the ECM to power down completely prior to the test procedure.
DTC P0121, P0122, P0123, P0221, P0222 or P0223 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 Quickly depress the accelerator pedal to wide-open throttle then release pedal. Repeat this procedure several times or operate
the vehicle within the conditions for running the DTC.
4 Using Tech 2, select the DTC display function.
Does DTC P0121, P0122, P0123, P0221, P0222 or P0223 fail this
ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 1 Disconnect the throttle actuator wiring connector.
2 Switch on the ignition with the engine not running.
3 Using a digital multimeter, measure the voltage between the TP sensor 5 V reference circuit and the ECM housing.
Does the multimeter display 4.8 – 5.2 V? Go to Step 4 Go to Step 7
4 1 Connect a 3 A fused jumper wire between the TP sensor 5 V
reference circuit and the TP sensor 1 signal circuit.
2 Switch on the ignition with the engine not running.
3 Using Tech 2, observe the TP sensor 1 voltage parameter.
Does Tech 2 display 4.8 – 5.2 V?
Go to Step 5 Go to Step 8
5 1 Connect a 3 A fused jumper wire between the TP sensor 5 V
reference circuit and the TP sensor 2 signal circuit.
2 Using Tech 2, observe the TP sensor 2 voltage parameter.
Does Tech 2 display 4.8 – 5.2 V?
Go to Step 6 Go to Step 9
6 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 TP 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 the test.
Does the multimeter display 5 Ω? Go to Step 11 Go to Step 10

BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007