Isuzu N-Series. Manual - part 791

Engine Control System (4JH1) 6E-215

Repair the open circuit or high resistance on the
control circuit of the MIL between the ECM (pin 42
of B-234 connector) and the IPC (pin 4 of B-51
connector).

Did you complete the repair?

—

Go to Step 19

—

Turn OFF the ignition.

Inspect for an intermittent and for poor
connections on the MIL circuits at the IPC
(pins 4 and 8 of B-51 connector).

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 16

Replace the MIL bulb. Did you complete the
replacement?

—

Go to Step 19

—

Repair or replace the IPC (meter assembly).

Did you complete the repair or replacement?

—

Go to Step 19

—

Turn OFF the ignition for 30 seconds.

Turn ON the ignition for 10 seconds, with the
engine OFF.

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

Does the DTC fail this ignition?

—

Go to Step 18

Go to Diagnostic

Aids

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 19

—

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

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 20

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

6E-216 Engine Control System (4JH1)

P1690 (Symptom Code 8) (Flash Code 77)

Circuit Description
The malfunction indicator lamp (MIL) is located on the
instrument panel cluster (IPC). The battery voltage is
supplied to the MIL. The engine control module (ECM)
turns the MIL ON by grounding the MIL control circuit.
After a fixed time passes, the ECM turns OFF the MIL
with the ignition ON and the engine OFF. The MIL has
the following functions:

• The MIL informs the driver that a malfunction has

occurred and the vehicle should be taken in for
service as soon as possible.

• The MIL illuminates during a bulb test and a

system test.

• A DTC will be stored if a MIL is requested by the

ECM.

If the ECM detects a short to battery or ignition voltage
on the MIL control circuit, this DTC will set.

Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects a high voltage condition on the

MIL control circuit for longer than 1 second when
the MIL is commanded ON.

Action Taken When the DTC Sets

• The ECM does not illuminates the MIL when the

diagnostic runs and fails.

Condition for Clearing the DTC

• 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.

Test Description
The number below refers to the step number on the
diagnostic table.
3. If the control circuit of the MIL between the ECM and
the IPC is normal, the control circuit voltage low DTC
P1690 (Symptom Code 4) will set.

DTC P1690 (Symptom Code 8) (Flash Code 77)
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

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic

System Check –

Engine Controls

Install the Tech 2.

Turn ON the ignition, with the engine OFF.

Perform the Malfunction Indicator Lamp (MIL)
test with the Tech 2.

Command the MIL ON with the Tech 2.

Does the MIL turn ON when commanded ON with
the Tech 2?

—

Go to Diagnostic

Aids

Go to Step 3

Turn OFF the ignition.

Remove the instrument panel cluster (IPC) in
order to disconnect the IPC harness B-51
connector.

Disconnect the IPC harness B-51 connector.

Turn ON the ignition, with the engine OFF.

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

Does DTC P1690 (Symptom Code 4) set, but not
DTC P1690 (Symptom Code 8)?

—

Go to Step 5

Go to Step 4

Test the control circuit of the MIL between the
engine control module (ECM) (pin 42 of B-234
connector) and the IPC (pin 4 of B-51
connector) for a short to battery or ignition
voltage.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 7

Go to Step 6

Engine Control System (4JH1) 6E-217

Repair or replace the IPC (meter assembly).

Did you complete the repair or replacement?

—

Go to Step 7

—

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

—

Reconnect all previously disconnected
harness connector(s).

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 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

6E-218 Engine Control System (4JH1)

Glow Control System Check

Description
The glow control system consists of the engine control
module (ECM), the glow relay and glow plugs. The
glow control system is operated when the engine
coolant temperature is low, which allows easier engine
starting. The ECM commands the glow relay ON for a
certain length of time at ignition switch is ON with
engine OFF. In after glow phase, the glow plugs
remain energized for a certain period with engine run.

Glow Control Operation

• The pre glow control system operates when the

engine coolant temperature is less than 30

°C

(86

°F).

• The after glow control system operates when the

engine coolant temperature is less than 30

°C

(86

°F).

Glow Control System Check
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic

System Check –

Engine Controls

Install the Tech 2.

Turn OFF the ignition for 30 seconds.

Turn ON the ignition, with the engine OFF.

Monitor the Diagnostic Trouble Code (DTC)
Information of the engine control system with
the Tech 2 and check whether following
DTC(s) is set:

• P0115 (Symptom Code 1 & 2)
• P0380 (Symptom Code 4 & 8)
• P0381 (Symptom Code 4 & 8)

Are any of the above DTC(s) set?

—

Refer to Applicable

DTC

Go to Step 3

Turn OFF the ignition.

Make sure the metal bus bar that connects
switched battery voltage supply terminal (J-
122) and all glow plugs is secured tightly.

Turn ON the ignition, with the engine OFF

Connect a test lamp between the metal bus
bar (glow plug power supply J-122 terminal)
and a known good ground.

Perform the Glow Relay test with the Tech 2.

Command the Glow Relay ON with the Tech 2
while observing the test lamp.

Does the test lamp turn ON only when commanded
ON with the Tech 2?

—

Go to Step 4

Go to Step 5

Turn OFF the ignition.

Remove the metal bus bar from the glow
plugs.

Measure resistance of each glow plug
between the glow plug terminals and a known
good ground. Make sure to record all
measurements and take them quickly as to
not allow engine temperature changes
between measurements.

Are the resistances within the specified value each
other?

Ω

System OK

Go to Step 15

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