Isuzu 4JA1 Workshop Manual page 478

6E-224 Engine Control System (4JH1)
DTC P1690 (Symptom Code 8) (Flash Code 77)
Circuit Description
The malfunction indicator lamp (MIL) is located on the
instrument panel (IP) cluster. 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.
Step
1 Did you perform the Diagnostic System Check-
Engine Controls?
2 1. Install the scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Perform the Malfunction Indicator Lamp (MIL)
test with the scan tool.
4. Command the MIL ON with the scan tool.
Does the MIL turn ON when commanded ON with
the scan tool?
3 1. Turn OFF the ignition.
2. Remove the instrument panel (IP) cluster in order
to disconnect the IP cluster harness B-23
connector.
3. Disconnect
connector.
4. Turn ON the ignition, with the engine OFF.
5. Monitor the Diagnostic Trouble Code (DTC)
Information with the scan tool.
Does DTC P1690 (Symptom Code 4) set, but not
DTC P1690 (Symptom Code 8)?
Action
the IP cluster harness
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 scan tool.
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 IP cluster is normal, the control circuit voltage low
DTC P1690 (Symptom Code 4) will set.
4. If the control circuit of the MIL between the ECM and
the IP cluster 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
Value(s)


B-23

Yes
Go to Diagnostic
System Check-
Go to Step 2 Engine Controls
Go to Diagnostic
Aids Go to Step 3
Go to Step 5 Go to Step 4
No