Isuzu KB P190. Manual — part 290

6E-126 Engine Control System (4JH1)

Step Action

Value(s)

Yes

No

4

1. Observe the Engine Speed parameter with the

scan tool.

2. Accelerate the engine between idle and W.O.T.

(accelerator pedal full travel) many times while
observing the scan tool.

Does the Engine Speed parameter indicate correct
engine speed?



Go to Step 9

Go to Step 5

5

1. Inspect the crankshaft position (CKP) sensor for

tightness.

2. Remove the CKP sensor and check for damage,

metal particles on magnet and for flywheel
circumference damage.

Did you find and correct the condition?



Go to Step 10

Go to Step 6

6

1. Turn OFF the ignition.
2. Disconnect the CKP sensor harness connector.
3. Inspect for an intermittent, for poor connections

and corrosion on the CKP sensor terminal (pins
1, 2 and 3 of E-9 connector).

4. Repair the connection(s) as necessary.
Did you find and correct the condition.



Go to Step 10

Go to Step 7

7

1. Turn OFF the ignition.
2. Disconnect the fuel injection pump control unit

(PCU) harness connector.

3. Inspect for an intermittent, for a poor connection

and corrosion on the CKP sensor signal input at
the harness connector of the PCU (pin 8 of E-6
connector).

4. Repair the connection(s) as necessary.
Did you find and correct the condition?



Go to Step 10

Go to Step 8

8

1. Turn OFF the ignition.
Disconnect the engine control module (ECM)
harness connector.
2. Inspect for an intermittent, for poor connections

and corrosion on at the harness connector of the
ECM (pins 90, 91, 98 and 101 of C-57
connector).

3. Repair the connection(s) as necessary.
Did you find and correct the condition?



Go to Step 10

Go to Step 9

9

Important: The fuel injection pump must be timed to
the engine.
Replace the fuel injection pump. Refer to Fuel
Injection Pump Replacement in engine mechanical
section.
Did you complete the replacement?



Go to Step 10



10

1. Reconnect all previously disconnected harness

connector(s).

2. Clear the DTCs with the scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine.
5. Accelerate the engine between idle and W.O.T.

(accelerator pedal full travel) many times while
observing the DTC Information with the scan
tool.

Does the DTC fail this ignition?



Go to Step 2

Go to Step 11

11

Observe the DTC Information with the scan tool.
Are there any DTCs that you have not diagnosed?



Go to Diagnostic

Trouble Code (DTC)

List System

OK

Engine Control System (4JH1) 6E-127

DTC P0251 (Symptom Code 9, A, B, C) (Flash Code 53)

Circuit Description
The engine control module (ECM) calculates the
desired fuel injection quantity and timing using data sent
from various sensors. These desired data are sent to
the fuel injection pump control unit (PCU) via a
controller area network (CAN) communication bus. The
PCU also receives signals from the internal inputs:
pump camshaft position (CMP) sensor that is located
inside the fuel injection pump to determine the cam ring
rotation angle and the fuel injection pump speed. The
fuel temperature (FT) sensor is internal the PCU. These
values are used to compare the desired values sent
from the ECM then PCU determines the injection timer
piston position and fuel injection quantity, and actuates
timing control valve (TCV) & fuel injection solenoid
valve based on control maps in the PCU.
The fuel injection solenoid valve is installed to the fuel
injection pump rear side. The fuel injection event is
determined by this solenoid ON/OFF command. The
fuel injection solenoid valve cuts the fuel when the
engine shutoff (ESO) solenoid valve is commanded
shutoff from the PCU. (The fuel injection solenoid valve
and engine shutoff (ESO) solenoid valve is same part. It
calls ESO solenoid valve when fuel is shutoff.) When
the ignition switch is turned OFF or commanded from
fail-safe action, the ESO solenoid valve is commanded
shutoff to stop the engine running.
Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The PCU detects internal fuel injection pump

control maps are not programmed during self-test.
(Symptom Code 9)

• The PCU detects internal EEPROM or A/D

converter is failed during self-test. (Symptom Code
A)

• The PCU detects that the fuel injection solenoid

valve drive circuit is failed during self-test.
(Symptom Code B)

• The PCU detects that the fuel injection solenoid

valve drive circuit voltage level is abnormal during
self-test. (Symptom Code D)

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM cuts fuel injection. (Symptom Code 9)
• The ECM limits fuel injection quantity. (Symptom

Code A)

Condition for Clearing the MIL/DTC

• The ECM turns OFF the MIL when the diagnostic

runs and does not fail.

• A history DTC clears after 40 consecutive driving

cycles without a fault. Or clear with the scan tool.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• Fuel injection solenoid valve is internal to the fuel

injection pump assembly.

• PCU is part of the fuel injection pump assembly.

DTC P0251 (Symptom Code 9, A, B, D) (Flash Code
53)

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 the scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Monitor the Diagnostic Trouble Code (DTC)

Information with the scan tool.

Does the DTC fail this ignition?



Go to Step 3

Go to Step 4

3

Important: The fuel injection pump must be timed to
the engine.
Replace the fuel injection pump. Refer to Fuel
Injection Pump Replacement in engine mechanical
section.
Did you complete the replacement?



Go to Step 4



6E-128 Engine Control System (4JH1)

Step Action

Value(s)

Yes

No

4

1. Clear the DTCs with the scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Monitor the DTC Information with the scan tool.
Did the DTC fail this ignition?



Go to Step 3

Go to Step 5

5

Observe the DTC Information with the scan tool.
Are there any DTCs that you have not diagnosed?



Go to Diagnostic

Trouble Code (DTC)

List System

OK

Engine Control System (4JH1) 6E-129

DTC P0251 (Symptom Code E) (Flash Code 53)

Circuit Description
The engine control module (ECM) calculates the
desired fuel injection quantity and timing using data sent
from various sensors. These desired data are sent to
the fuel injection pump control unit (PCU) via a
controller area network (CAN) communication bus. The
PCU also receives signals from the internal inputs:
pump camshaft position (CMP) sensor that is located
inside the fuel injection pump to determine the cam ring
rotation angle and the fuel injection pump speed. The
fuel temperature (FT) sensor is internal the PCU. These
values are used to compare the desired values sent
from the ECM then PCU determines the injection timer
piston position and fuel injection quantity, and actuates
timing control valve (TCV) & fuel injection solenoid
valve based on control maps in the PCU.
The ECM monitors CAN operational status by expecting
a constant flow of messages from the PCU. If the ECM
detects that the communication message from the PCU
is not received, this DTC will set.
Condition for Running the DTC

The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects communication message from

the PCU is not received for longer than 1 second.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM cuts fuel injection.

Condition for Clearing the MIL/DTC

• The ECM turns OFF the MIL when the diagnostic

runs and does not fail.

• A history DTC clears after 40 consecutive driving

cycles without a fault. Or clear with the scan tool.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• PCU is part of the fuel injection pump assembly.

DTC P0251 (Symptom Code E) (Flash Code 53)

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 the scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine. If the engine does not start,

crank over the engine.

4. Monitor the Diagnostic Trouble Code (DTC)

Information with the scan tool.

Is DTC P1650 (Symptom Code A or B) or P1651
(Symptom Code A or B) set?



Go to Applicable

DTC

Go to Step 3

3

1. Turn ON the ignition, with the engine OFF.
2. Monitor the DTC Information with the scan tool.
Does the DTC fail this ignition?



Go to Step 4

Go to Step 5

4

Important: Replacement ECM must be
programmed.
Replace the ECM. Refer to Engine Control Module
(ECM) Replacement in this section.
Did you complete the replacement?



Go to Step 5



5

1. Clear the DTCs with the scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Monitor the DTC Information with the scan tool.
Does the DTC fail this ignition?



Go to Step 2

Go to Step 6

6

Observe the DTC Information with the scan tool.
Are there any DTCs that you have not diagnosed?



Go to Diagnostic

Trouble Code (DTC)

List System

OK