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Isuzu KB P190. Manual - part 853

Engine Management – V6 – Diagnostics

Page 6C1-2–134

Test Description

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

A fault condition in the stop lamp switch assembly may trigger these DTCs.

DTC P0504 or P0571 Diagnostic Table

Step Action

Yes

Has the diagnostic system check been performed?

Go to Step 2

Refer to

4.4 Diagnostic

System Check in

this Section

Switch off the ignition for 30 seconds.

Operate the vehicle within the conditions for running the DTC.

Using Tech 2, select the DTC display function.

Does DTC P0504 or DTC P0571 fail this ignition cycle?

Go to Step 3

Refer to Additional

Information in this

DTC

Ignition ON, engine OFF.

On Tech 2 select: Engine / V6 Engine / Data Display / Cruise
Control Data.

Observe the status of the brake lamp switch and cruise control
cancel switch.

Fully depress the brake pedal.

Does Tech 2 display change from Inactive to Active in all switches
when the pedal is pressed?

Refer to Additional

Information in this

DTC

Go to Step 4

Did the brake lamp switch Tech 2 status fail to change?

Go to Step 5

Go to Step 9

Disconnect the wiring connector from the brake switch
assembly. Refer to 8C Cruise Control.

2 Ignition

ON.

Connect a test lamp between the voltage circuit of the stop
lamp switch and a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 6

Repair the high resistance or open circuit fault condition in the
voltage circuit of the stop lamp switch. Refer to 8A Electrical -
Body and Chassis for information on electrical wiring repair
procedures.

Was the repair completed?

Go to Step 14

—

Test the stop lamp switch. Refer to 8C Cruise Control – HFV6.

Was any fault found and rectified?

Go to Step 14

Go to Step 8

Test the control circuit of the stop lamp switch 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 the repair completed?

Go to Step 14

Go to Step 13

Disconnect the wiring connectors from the brake switch
assembly. Refer to 8C Cruise Control – HFV6.

2 Ignition

ON.

Connect a test lamp between the voltage circuit of the cruise
control cancel switch and a good ground.

Does the test lamp illuminate?

Go to Step 11

Go to Step 10

Engine Management – V6 – Diagnostics

Page 6C1-2–135

Step Action

Yes

10 1

Repair the high resistance or open circuit fault condition in the
voltage circuit of the cruise control cancel switch. Refer to 8A
Electrical - Body and Chassis for information on electrical wiring
repair procedures.

Was the repair completed?

Go to Step 14

—

11 1

Test the cruise control cancel switch. Refer to 8C Cruise Control
– HFV6.

Was any fault found and rectified?

Go to Step 14

Go to Step 12

12 1

Test the control circuits of the cruise control cancel switch 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 the repair completed?

Go to Step 14

Go to Step 13

13 1

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

Was the repair completed?

Go to Step 14

—

14 1

Using Tech 2, clear the DTCs.

Switch off the ignition for 30 seconds.

Start the engine.

Operate the vehicle within the conditions for running the DTC.

Does DTC P0504 or P571 fail this ignition cycle?

Go to Step 2

15 1

Using Tech 2, select the DTC display function.

Are there any DTCs displayed?

Go to the

appropriate DTC

Table in this Section

System OK

When all diagnosis and repairs are completed, check the system for correct operation.

7.29 DTC P0506, P0507, P0638, P1551, P2100,

P2101, P2119 or P2176

DTC Descriptors

This diagnostic procedure supports the following DTCs:

•

DTC P0506 – Idle Speed Control rpm Too Low

•

DTC P0507 – Idle Speed Control rpm Too High

•

DTC P0638 – Commanded Versus Actual Throttle Position Correlation

•

DTC P1551 – Throttle Control Lower Position Not Reached During Learning Mode

•

DTC P2100 – Throttle Control Motor Malfunction

•

DTC P2101 – Throttle Control Position Range / Performance

•

DTC P2119 – Closed Throttle Position Range / Performance

•

DTC P2176 – Throttle Control Lower Position not Learned

Circuit Description

The ECM monitors and evaluates the accelerator pedal position (APP) sensors signal voltage along with other sensor
inputs to determine the desired throttle opening. To control the throttle plate movement, the ECM applies a pulse width
modulated (PWM) signal voltage to the throttle actuator motor through the throttle actuator motor control circuits.

•

At engine idle speed or when no current is flowing into the throttle actuator motor, a constant force return spring
holds the throttle plate at a constant seven percent throttle opening position.

Engine Management – V6 – Diagnostics

Page 6C1-2–136

•

To control the throttle opening, the ECM applies PWM voltage to the throttle actuator motor. The ECM increases
this PWM voltage duty cycle to increase the throttle opening.

•

To decrease the throttle opening from the seven percent rest position, the ECM reverses the polarity of the throttle
actuator motor control circuit then applies a PWM voltage to the throttle actuator motor.

In addition, the ECM monitors the signal voltage applied to the throttle actuator motor control circuit. A TAC motor
control circuit DTC sets if the ECM detects a fault condition in the TAC circuits or motor performance.

Conditions for Running the DTC

DTC P0506 and P0507

Runs continuously once the following conditions are met:

•

DTCs P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0221, P0222, P0223, P0443, P0446, P0455, P0458
and P0459 are not set.

•

The ignition is switched on.

•

The vehicle speed is 0 km/h.

•

The engine coolant temperature is greater than 60

°C.

•

The intake air temperature is greater than -10.5

°C.

•

The volumetric efficiency is less than 35 percent.

•

The EVAP purge solenoid is off.

DTC P0638

Runs continuously once the following conditions are met:

•

The ignition is switched on.

•

The ignition voltage is greater than 7 V.

DTC P2100

Runs continuously once the following conditions are met:

•

DTC P2101 ran and passed.

•

The ignition is switched on.

DTC P2101

Runs continuously once the following conditions are met:

•

The battery voltage is greater than 7 V.

•

The ignition is switched on.

DTC P1551, P2119 and P2176

Runs continuously once the following conditions are met:

•

The ignition is switched on.

•

The vehicle speed is 0 km/h.

•

The engine speed is less than 40 rpm

•

The engine coolant temperature is 5 – 60

°C.

•

The intake air temperature is 5 – 60

°C.

•

The ignition voltage is greater than 10 V.

•

The APP is less than 15 percent.

Engine Management – V6 – Diagnostics

Page 6C1-2–137

Conditions for Setting the DTC

DTC P0506

The actual engine speed is less than the desired idle speed by at least 100 rpm for 10 seconds.

DTC P0507

The actual engine speed is greater than the desired idle speed by at least 200 rpm for 10 seconds or the ECM detects
three fuel cut-offs due to an engine over speed condition while the engine is idling.

DTC P0638

The ECM detects the commanded duty cycle is greater than 80 percent for longer than 0.6 second.

DTC P1551

The ECM detects the TP sensor angle is outside the predetermined range of 1.8 – 13.0 percent when the TAC motor is
deactivated.

DTC 2100

The ECM detects that its internal TAC motor output driver does not deactivate when commanded off.

DTC P2101

The ECM detects the difference between the commanded and the actual throttle opening is greater than 10 percent.

DTC P2119

The ECM determines the throttle plate didn't return to the rest position within 720 milliseconds.

DTC P2176

One of the following conditions exist:

•

The TP sensor 1 voltage is outside the range of 0.2 – 0.9 V during the throttle learn procedure.

•

The TP sensor 2 voltage is outside the range of 4.2 – 4.8 V during the throttle learn procedure.

•

The throttle learn procedure is not learned after an ECM replacement.

Conditions for Clearing DTC

The TAC motor control circuit DTCs are Type A DTCs. Refer to 1.4 Diagnostic Trouble Codes in this Section, for
action taken when a Type A DTC sets and conditions for clearing Type A DTCs.

Additional Information

•

Refer to 6C1-1 Engine Management – V6 – General Information for details of the Throttle Actuator Control System
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 numbers refer to the step numbers in the diagnostic table:

A constant force return spring holds the throttle plate at a constant seven percent throttle opening position and
should move in either direction under spring pressure and without binding.

When the ignition is switched on, the ECM operates the throttle actuator motor to verify the integrity of the TAC
system prior to start up. This can be seen by the momentary flash of the test lamp as the ignition is switched on.

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