Isuzu 4JA1 Workshop Manual page 475

DTC P1690 (Symptom Code 4) (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 an open circuit or short circuit on the
MIL control circuit, this DTC will set.
Condition for Running the DTC
• The ignition switch is 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 Command the MIL OFF with the scan tool.
Does the MIL OFF?
4 1. Turn OFF the ignition.
2. Inspect the Meter (10A) fuse (C-14) in the cabin
fuse block.
Is the Meter (10A) fuse (C-14) open?
5 Replace the Meter (10A) fuse (C-14). If the fuse
continues to open, repair the short to ground on one
of the circuits that fed by the Meter (10A) fuse (C-14)
or replace the shorted attached component fed by
the Meter (10A) fuse (C-14).
Did you complete the repair?
6 1. Turn OFF the ignition.
2. Disconnect the engine control module (ECM)
harness connector.
3. Turn ON the ignition, with the engine OFF.
4. Connect a 3-amp fused jumper wire between the
MIL control circuit of the ECM harness connector
(pin 39 of C-56 connector) and a known good
ground.
Does the MIL illuminate?
Action
Engine Control System (4JH1) 6E-221
Condition for Setting the DTC
• The ECM detects a low voltage condition on the
MIL control circuit for longer than 3 seconds when
the MIL is commanded OFF.
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.
DTC P1690 (Symptom Code 4) (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) Yes

Go to Step 2
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Go to Step 3
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Go to Step 17
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Go to Step 5
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Go to Step 17
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Go to Step 10
No
Go to Diagnostic
System Check-
Engine Controls
Go to Step 4
Go to Step 9
Go to Step 6
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Go to Step 7