Isuzu N-Series. Manual - part 788

 Engine Control System (4JH1)    6E-203

7

Replace the ECM main relay.

Did you complete the replacement?

—

Go to Step 9

—

8

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 9

—

9

1.

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

2.

Clear the DTCs with the Tech 2.

3.

Turn OFF the ignition for 30 seconds.

4.

Monitor the DTC Information with the Tech 2.

Does the DTC with the ignition switch OFF?

—

Go to Step 3

Go to Step 10

10

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-204    Engine Control System (4JH1) 

P1630 (Symptom Code A, B) (Flash Code 51)

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.  If the
ECM detects that the fuel injection solenoid valve
control current problem, this DTC will set.

Condition for Setting the DTC

• The ECM detects that the PCU monitored fuel

injection solenoid valve control current is too high.
(Symptom Code A)

• The ECM detects that the PCU continuously flow

the control current to the fuel injection solenoid
valve.  (Symptom Code B)

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.  (Symptom

Code A)

• The ECM cuts fuel injection.  (Symptom Code B)

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 solenoid valve is internal to the fuel

injection pump assembly.

• PCU is part of the fuel injection pump assembly.

DTC P1630 (Symptom Code A, B) (Flash Code 51)

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

—

 Engine Control System (4JH1)    6E-205

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.

Did 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

Step

Action

Value(s)

Yes

No

6E-206    Engine Control System (4JH1) 

P1650 (Symptom Code A) (Flash Code 44)

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 PCU receives from the CAN
controller rest or Bus Offline, this DTC will set.

Condition for Setting the DTC

• The ECM detects that the PCU receives from the

CAN controller reset or Bus Offline.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM cuts the 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 Tech 2.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

DTC P1650 (Symptom Code A) (Flash Code 44)
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 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 Tech 2.

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

—

Go to Applicable 

DTC

Go to Step 3

3

Monitor the DTC Information with the Tech 2.

Does the DTC fail this ignition?

—

Go to Step 4

Go to Diagnostic 

Aids

4

1.

Turn OFF the ignition.

2.

Disconnect the fuel injection pump control unit
(PCU) harness connector.

3.

Connect a DMM across the controller area
network (CAN) harness (pins 1 and 2 of E-110
connector).

4.

Measure the resistance across the CAN
terminals.

Is the resistance within the specified value?

110 – 130 

Ω

Go to Step 5

Go to Step 10

5

1.

Connect a DMM between the CAN Low signal
circuit (pin 1 of E-110 connector) and a known
good ground.

2.

Turn ON the ignition, with the engine OFF.

Is the DMM voltage within the specified value?

1.5 – 2.5 volts

Go to Step 6

Go to Step 11