Isuzu N-Series. Manual - part 784

 Engine Control System (4JH1)    6E-187

10

1.

Reconnect all previously disconnected
harness connector(s).

2.

Clear the DTCs with the Tech 2.

3.

Turn OFF the ignition for 30 seconds.

4.

Start the engine.

5.

Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 11

11

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic 

Trouble Code (DTC) 

List

System OK

Step

Action

Value(s)

Yes

No

6E-188    Engine Control System (4JH1) 

P1345 (Symptom Code A) (Flash Code 41)

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
PCU also compares the engine speed signal sent from
the ECM and the fuel injection pump speed.  If the PCU
received faulty fuel injection pump CMP sensor signal,
this DTC will set.

Condition for Setting the DTC

• The PCU received faulty fuel injection pump CMP

sensor signal for 1 second.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM limits fuel injection quantity.

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 Tech 2.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• Fuel injection pump CMP sensor is internal to the

fuel injection pump assembly.

• PCU is part of the fuel injection pump assembly.

DTC P1345 (Symptom Code A) (Flash Code 41)

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 Tech 2.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Monitor the Diagnostic Trouble Code (DTC)
Information with the Tech 2.

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

—

4

1.

Clear the DTCs with the Tech 2.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Monitor the DTC Information with the Tech 2.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Step 5

5

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic 

Trouble Code (DTC) 

List

System OK

 Engine Control System (4JH1)    6E-189

P1520 (Symptom Code A) (Flash Code 47)

Circuit Description
The neutral switch is installed on the transmission gear
control box.  When the gear position is neutral, the
switch is closed and the switch signal is provided to the
engine control module (ECM).  If the ECM detects the
neutral switch signal is not changed from neutral during
the predetermined engine speed and vehicle speed
range, this DTC will set.

Condition for Running the DTC

• The ignition switch is ON.
• The engine speed is higher than 1500 RPM.
• The vehicle speed is higher than 64 km/h (40

MPH).

• The clutch pedal is released.

Condition for Setting the DTC

• The ECM detects that the neutral switch signal is

continuously ON (neutral) during three consecutive
driving cycles.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

Condition for Clearing the MIL/DTC
Important:

• Following conditions must be met two consecutive

driving cycles.  (One driving cycle: Ignition switch
ON > Engine run > Vehicle run > Ignition switch
OFF for 10 seconds)

- The engine speed is higher than 1500 RPM
- The vehicle speed is higher than 64 km/h (40

MPH)

- The clutch pedal is released
- Other than neutral

• After the above procedure is done, a history DTC

clears after 40 consecutive driving cycles without a
fault.  Or clear with the Tech 2.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

DTC P1520 (Symptom Code A) (Flash Code 47)
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

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 Tech 2.

2.

Turn ON the ignition, with the engine OFF.

3.

Observe the Neutral Switch parameter with
the Tech 2 while shift to neutral and other
positions.

Does the Tech 2 indicate ON when the position is
neutral and OFF when other than the neutral?

—

Go to Diagnostic 

Aids

Go to Step 3

3

1.

Turn OFF the ignition.

2.

Disconnect the neutral switch harness
connector.

3.

Turn ON the ignition, with the engine OFF.

4.

Observe the Neutral Switch parameter with
the Tech 2.

Does the Tech 2 indicate ON?

—

Go to Step 4

Go to Step 5

4

1.

Test the neutral switch input signal circuit
between the engine control module (ECM)
(pin 87 of B-233 connector) and the neutral
switch (pin 2 of J-50 connector) 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 neutral switch.  Refer to Neutral Switch
Replacement in Transmission Section.

Did you complete the replacement?

—

Go to Step 7

—

6E-190    Engine Control System (4JH1) 

6

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 7

—

7

1.

Reconnect all previously disconnected
harness connector(s).

2.

Clear the DTCs with the Tech 2.

Important:
Following conditions must be met two consecutive
driving cycles before clear with the Tech 2.  (One
driving cycle: Ignition switch ON > Engine run >
Vehicle run > Ignition switch OFF for 10 seconds)

• The engine speed is higher than 1500 RPM
• The vehicle speed is higher than 64 km/h (40

MPH)

• The clutch pedal is released
• Other than neutral

3.

Turn ON the ignition, with the engine OFF.

4.

Observe the Neutral Switch parameter with
the Tech 2 while shift to neutral and other
positions.

Does the Tech 2 indicate ON when the position is
neutral and OFF when other than the neutral?

—

Go to Step 8

Go to Step 3

8

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic 

Trouble Code (DTC) 

List

System OK

Step

Action

Value(s)

Yes

No