Isuzu KB P190. Manual — part 861

Engine Management – V6 – Diagnostics

Page 6C1-2–166

Test Description

The following numbers refer to the step numbers in the diagnostic table:

4

This step tests the ECM ground circuits and supply voltage.

DTC P1648 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

Using Tech 2, select the DTC display function.

N O T E

Do not attempt to perform any Tech 2 function that
requires the ECM security code to be entered.

Does DTC P1648 fail this ignition cycle?

Go to Step 4

Go to Step 3

3

Using Tech 2, attempt a programming function that requires the ECM
security code to be entered. Refer to 6C1-3 Engine Management –V6
– Service Operations for details on resetting the ECM.

Has the programming function been successfully performed?

System OK

Go to Step 4

4

1

Test all ECM ground circuits for a high resistance or an open
circuit fault condition. Refer to 8A Electrical - Body and Chassis
for information on electrical fault diagnosis.

2

Test the ECM ignition supply voltage circuit for a high
resistance, open circuit or short to ground fault condition. Refer
to 8A Electrical - Body and Chassis for information on electrical
fault diagnosis.

Has any fault been found and rectified?

Go to Step 6

Go to Step 5

5

Replace the ECM. Refer to 6C1-3 Engine Management –V6 – Service
Operations for details on replacing the ECM.

Has the repair been completed?

Go to Step 6

—

6

1

Using Tech 2, clear the DTCs.

2

Switch off the ignition for 30 seconds.

Does DTC P1648 fail this ignition cycle?

Go to Step 2

Go to Step 7

7

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, clear all DTCs and check the system for correct operation.

7.44 DTC P1668, P2500 or P2501

DTC Descriptors

This diagnostic procedure supports the following DTCs:

•

DTC P1668 – Generator L Terminal Circuit Malfunction

•

DTC P2500 – Generator L Terminal Low Voltage

•

DTC P2501 – Generator L Terminal High Voltage

Engine Management – V6 – Diagnostics

Page 6C1-2–167

Circuit Description

The engine control module (ECM) applies a signal voltage to the Generator L (GEN L) terminal circuit to control the load
of the generator on the engine. Refer to 6D1-1 Charging System for details of the charging system operation.

A GEN L terminal circuit DTC sets if the ECM detects the Gen L circuit voltage is outside the specified range for a
predetermined set of parameters.

Conditions for Running the DTC

DTC P1668

Runs continuously when one of the following conditions are met:

•

Ignition on Test – The ignition is switched on with the engine not running for 5 seconds.

•

Engine Run Test – The engine is running at speed less than 3,000 rpm

DTC P2500

Runs continuously when the following conditions are met:

•

There is no generator, CKP sensor or CMP sensor DTC set.

•

The engine is running.

•

The generator is not commanded off.

DTC P2501

Runs continuously when the following conditions are met:

•

There is no generator, CKP sensor or CMP sensor DTC set.

•

The ignition is switched on with the engine not running.

Conditions for Setting the DTC

DTC P1668

•

Ignition on Test – the ECM detects a high signal voltage on the Gen L for 5 seconds.

•

Engine Run Test – the ECM detects a low signal voltage on the Gen L for 5 seconds.

DTC P2500

The ECM detects a low signal voltage on the Gen L for 15 seconds.

DTC P2501

The ECM detects a high signal voltage on the Gen L for 5 seconds.

Conditions for Clearing DTC

The Generator L-terminal circuit are Type C DTCs. Refer to 1.4 Diagnostic Trouble Codes in this Section, for action
taken when a Type C DTC sets and conditions for clearing Type C DTCs.

Additional Information

•

For an intermittent fault condition, refer to 5.2

Intermittent Fault Conditions in this Section.

•

Refer to 6C1-1 Engine Management – V6 – General Information for details of the ECM operation.

•

Refer to 6D1-1 Charging System – V6 for details of the charging system operation.

•

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.

Engine Management – V6 – Diagnostics

Page 6C1-2–168

•

To assist diagnosis, refer to 3

Wiring Diagrams and Connector Charts in this Section, for the system wiring

diagram and connector charts.

DTC P1668, P2500 or P2501 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 P1668, P2500 or P2501 fail this ignition cycle?

Go to Step 3

Refer to Additional

Information in this

DTC

3

Test the charging system for any fault condition that may cause
incorrect generator operation. Refer to 6D1-1 Charging System – V6.

Was any fault found and rectified?

Go to Step 6

Go to Step 4

4

Test the Gen L 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.

Was any fault found and rectified?

Go to Step 6

Go to Step 5

5

Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.

Was the repair completed?

Go to Step 6

—

6

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 Generator L terminal circuit DTCs fail this ignition
cycle?

Go to Step 2

Go to Step 7

7

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.

7.45 DTC

P1845

DTC Descriptor

This diagnostic procedure supports DTC P1845 – Engine Torque Reduction Malfunction

Circuit Description

The ECM monitors and compares the engine torque output against the maximum allowable engine torque. Refer to
6C1-1 Engine Management – V6 – General Information for details of the engine torque limit management operation.

If the requested torque is higher than the maximum allowable torque, the ECM applies engine torque limitation and DTC
P1845 – Engine Torque Reduction Malfunction sets.

Conditions for Running the DTC

DTC P1845 runs continuously when the engine is running at speeds greater than 40 rpm.

Engine Management – V6 – Diagnostics

Page 6C1-2–169

Conditions for Setting the DTC

The engine torque output exceeds the maximum allowable torque output for 10 minutes.

Conditions for Clearing the DTC

DTC P1845 – Engine Torque Reduction Malfunction is a Type ‘C’ DTC. Refer to 1.4

Diagnostic Trouble Codes in this

Section, for action taken when a Type ‘C’ DTC sets and conditions for clearing Type ‘C’ DTC.

Additional Information

•

Refer to 6C1-1 Engine Management – V6 – General Information for details of the Engine Torque Limit
Management operation.

•

For an intermittent fault condition, refer to 5.2

Intermittent Fault Conditions in this Section.

•

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 Wiring Diagrams and Connector Charts in this Section, for the system wiring
diagram and connector charts.

Test Description

The following number refers to the step number in the diagnostic table:

4

Fault conditions that apply excessive load on the engine may trigger this DTC.

DTC P1845 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 or
road test the vehicle under various driving condition.

3

Using Tech 2, select the DTC display function.

Does DTC P1845 fail this ignition cycle?

Go to Step 3

Refer to Additional

Information in this

DTC

3

Are there any other ECM or TCM DTCs set?

Refer to the

appropriate DTC

table.

Go to Step 4

4

Inspect for fault conditions in the engine or transmission that applies
excessive load on the engine.

Was any fault found and rectified?

Go to Step 6

Go to Step 5

5

Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.

Was the repair completed?

Go to Step 6

—

6

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 DTC P1845 fail this ignition cycle?

Go to Step 2

Go to Step 7