Isuzu KB P190. Manual — part 439

ENGINE CONTROL SYSTEM (4JK1/4JJ1) 6E-139

DTC P0231 or P0232 (Flash Code 69)

Circuit Description

The ECM controls the fuel pump relay which supplies
power to the fuel pump in the fuel tank. The ECM
commands the fuel pump relay ON for a certain length
of time at ignition switch is ON with the engine OFF.
During the engine running it is continuously
commanded ON. If the ECM detects an improper
voltage level on the relay control circuit, DTC P0231 or
P0232 will set.

Condition for Running the DTC

• The battery voltage is more than 9 volts.

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects a low voltage condition on the

fuel pump relay control circuit for longer than 3
second when the relay is commanded OFF. (DTC
P0231)

• The ECM detects a high voltage condition on the

fuel pump relay control circuit for longer than 3
second when the relay is commanded ON. (DTC
P0232)

Action Taken When the DTC Sets

• The ECM illuminates the SVS lamp when the

diagnostic runs and fails. Refer to DTC Type
Definitions for Action Taken When the DTC Sets -
Type C. (Euro 4 Specification)

• The ECM illuminates the MIL when the diagnostic

runs and fails. Refer to DTC Type Definitions for
Action Taken When the DTC Sets - Type A.
(Except Euro 4 Specification)

• The ECM limits fuel injection quantity.

• The ECM inhibits cruise control.

Condition for Clearing the DTC

• Refer to DTC Type Definitions for Condition for

Clearing the SVS Lamp/ DTC - Type C. (Euro 4
Specification)

• Refer to DTC Type Definitions for Condition for

Clearing the MIL/ DTC - Type A. (Except Euro 4
Specification)

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• The fuel pump relay is commanded ON for 12

seconds at ignition switch is ON with the engine
OFF.

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views

Circuit/ System Testing DTC P0231

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check -
Engine Controls?

—

Go to Step 2

Go to Diagnostic

System Check -
Engine Controls

2

1.

Install a scan tool.

2.

Turn OFF the ignition for 30 seconds.

3.

Turn ON the ignition for 20 seconds while
observing the DTC Information with a scan
tool.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic

Aids

3

1.

Turn OFF the ignition.

2.

Replace the fuel pump relay with the head
light relay or replace with a known good relay.

3.

Turn ON the ignition for 20 seconds while
observing the DTC Information with a scan
tool.

Does the DTC fail this ignition?

—

Go to Step 4

Go to Step 7

6E-140 ENGINE CONTROL SYSTEM (4JK1/4JJ1)

4

1.

Turn OFF the ignition.

2.

Remove the fuel pump relay.

3.

Probe the ignition voltage feed circuit of the
relay coil side (pin 3 of X-13) with a test lamp
that is connected a known good ground.

4.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 5

Go to Step 6

5

1.

Test the control circuit between the ECM (pin
54 of C-58) and the relay (pin 5 of X-13) for
the following conditions:

• An open circuit

• A short to ground

• High resistance

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 11

Go to Step 8

6

Repair the open circuit or high resistance between
the ECM main relay (pin 1 of X-12) and the fuel
pump relay (pin 3 of X-13).

Did you complete the repair?

—

Go to Step 11

—

7

1.

Remove the fuel pump relay.

2.

Inspect for an intermittent and for a poor
connection on each relay terminal.

3.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 11

Go to Step 9

8

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connector.

3.

Inspect for an intermittent and for a poor
connection at the harness connector of the
ECM (pin 54 of C-58).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 11

Go to Step 10

9

Replace the fuel pump relay.

Did you complete the replacement?

—

Go to Step 11

—

10

Important: Replacement ECM must be
programmed and learned.
Replace the ECM. Refer to ECM Replacement.

Did you complete the replacement?

—

Go to Step 11

—

11

1.

Reconnect all previously disconnected fuse,
relay or harness connector(s).

2.

Clear the DTCs with a scan tool.

3.

Turn OFF the ignition for 30 seconds.

4.

Turn ON the ignition for 20 seconds while
observing the DTC Information with a scan
tool.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 12

12

Observe the DTC Information with a scan tool.

Are there any DTCs that you have not diagnosed?

—

Go to DTC List

System OK

Step

Action

Value(s)

Yes

No

ENGINE CONTROL SYSTEM (4JK1/4JJ1) 6E-141

Circuit/ System Testing DTC P0232

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check -
Engine Controls?

—

Go to Step 2

Go to Diagnostic

System Check -
Engine Controls

2

1.

Install a scan tool.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Monitor the DTC Information with a scan tool.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic

Aids

3

1.

Turn OFF the ignition.

2.

Replace the fuel pump relay with the head
light relay or replace with a known good relay.

3.

Start the engine.

4.

Monitor the DTC Information with a scan tool.

Does the DTC fail?

—

Go to Step 4

Go to Step 5

4

1.

Test the control circuit between the ECM (pin
54 of C-58) and the relay (pin 5 of X-13) for a
short to battery or ignition voltage.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 7

Go to Step 6

5

Replace the fuel pump relay.

Did you complete the replacement?

—

Go to Step 7

—

6

Important: Replacement ECM must be
programmed and learned.
Replace the ECM. Refer to ECM Replacement.

Did you complete the replacement?

—

Go to Step 7

—

7

1.

Reconnect all previously disconnected relay
or harness connector(s).

2.

Clear the DTCs with a scan tool.

3.

Turn OFF the ignition for 30 seconds.

4.

Start the engine.

5.

Operate the vehicle within the Conditions for
Running the DTC. You may also operate the
vehicle within the conditions that you
observed from the Freeze Frame/ Failure
Records.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 8

8

Observe the DTC Information with a scan tool.

Are there any DTCs that you have not diagnosed?

—

Go to DTC List

System OK

6E-142 ENGINE CONTROL SYSTEM (4JK1/4JJ1)

DTC P0234 (Flash Code 42)

Circuit Description

The boost pressure sensor is located in the air
induction tubing. The sensor is a transducer that varies
voltage according to changes in the air pressure inside
the air tubing. The ECM monitors the boost pressure
sensor signal for abnormal values. If the ECM detects
that the sensor signal is excessively high, this DTC will
set. This indicates excessive high boost pressure.

Condition for Running the DTC

• DTCs P0045, P0107 and P0108 are not set.

• The ignition switch is ON.

• The engine is running.

Condition for Setting the DTC

• The ECM detects that the actual boost pressure is

more than 20 kPa (3 psi) over the desired boost
pressure under certain conditions for longer than
10 seconds.

Action Taken When the DTC Sets

• The ECM illuminates the MIL when the diagnostic

runs and fails. Refer to DTC Type Definitions for
Action Taken When the DTC Sets - Type A.

• The ECM limits fuel injection quantity.

• The ECM inhibits pilot injection.

Condition for Clearing the DTC

• Refer to DTC Type Definitions for Condition for

Clearing the MIL/ DTC - Type A.

• The ECM limits fuel injection quantity.

• The ECM inhibits pilot injection.

• The ECM inhibits cruise control.

Diagnostic Aids

• An open circuit or high resistance in the boost

pressure low reference circuit may set this DTC.

• Misrouted vacuum hoses may set this DTC.

• Check the turbocharger nozzle control actuator for

a sticking. Refer to Turbocharger in the Engine
Mechanical section.

• Use a scan tool to verify the integrity of the boost

pressure sensor signal. Compare the Boost
Pressure to the Desired Boost Pressure under all
load conditions for an excessively high value.

• The fuel with which gasoline was mixed may set

this DTC.

Test Description

The numbers below refer to the step number on the
Circuit/ System Testing.
3. A skewed boost pressure sensor value (shifted to a
higher pressure) can set this DTC. The Boost Pressure
on the scan tool should read near Barometric Pressure
(BARO) with the key ON and engine OFF.
4. A skewed BARO sensor value (shifted to a lower
pressure) may indicate a wrong boost pressure. The
BARO on the scan tool should read near surrounding
barometric pressure.

Schematic Reference: Vacuum Hose Routing
Diagram and Engine Controls Schematics

Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views

Circuit/ System Testing DTC P0234

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check -
Engine Controls?

—

Go to Step 2

Go to Diagnostic

System - Check
Engine Controls

2

1.

Install a scan tool.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Monitor the DTC Information with a scan tool.

Is DTC P0045, P0107, P0108, P0638, P1196,
P1197, P1198, P2227, P2228 or P2229 also set?

—

Go to Applicable

DTC

Go to Step 3

3

1.

Turn ON the ignition, with the engine OFF.

2.

Observe the Boost Pressure and Barometric
Pressure (BARO) with a scan tool.

Does the scan tool indicate that the difference
between the Boost Pressure and BARO is more
than the specified value?

10 kPa (1.5

psi)

Go to Step 4

Go to Step 5