Isuzu 4JA1 Workshop Manual page 377

DTC P0380 (Symptom Code 4) (Flash Code 66)
Circuit Description
The engine control module (ECM) controls the glow
relay which supplies power to the glow plugs based on
engine coolant temperature. In the after glow phase, the
glow indicator light is not illuminated but glow plugs
remain active for a certain period. If the ECM detects an
open circuit or short to ground on the glow relay control
circuit, this DTC will set.
Condition for Running the DTC
• The ignition switch is ON.
Condition for Setting the DTC
• The ECM detects that the low voltage condition on
the glow relay control circuit for longer than 3
seconds when the relay is commanded OFF.
Action Taken When the DTC Sets
• The ECM illuminates the malfunction indicator
lamp (MIL) when the diagnostic runs and fails.
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 Glow Relay test with the scan tool.
4. Command the Glow Relay ON with the scan tool.
Does the glow relay click when commanded ON with
the scan tool?
3 1. Turn OFF the ignition.
2. Replace the glow relay with the starter relay or
replace with a known good relay.
3. Turn ON the ignition, with the engine OFF.
4. Command the Glow Relay ON with the scan tool.
Does the glow relay click when commanded ON with
the scan tool?
4 1. Turn OFF the ignition.
2. Inspect the ECM (10A) fuse (EB-4) in the engine
room fuse block.
Is the ECM (10A) fuse (EB-4) open?
5 Replace the ECM (10A) fuse (EB-4). If the fuse
continues to open, repair the short to ground on one
of the circuits that is fed by the ECM (10A) fuse (EB-
4) or replace the shorted attached component fed by
the ECM (10A) fuse (EB-4).
Did you complete the repair?
6 1. Turn OFF the ignition.
2. Remove the glow relay.
3. Connect a test lamp between the voltage feed
circuit of the glow relay coil side (pin 2 of X-5
connector) and a known good ground.
4. Turn ON the ignition, with the engine OFF.
Does the test lamp illuminate?
Action
Engine Control System (4JH1) 6E-123
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 scan tool.
Notice:
• The glow relay is commanded OFF with ignition
ON and engine OFF when the engine coolant
temperature is reached at 30°C (86°F).
• The glow relay is commanded OFF with engine
run when the engine coolant temperature is
reached at 60°C (140°F).
DTC P0380 (Symptom Code 4) (Flash Code 66)
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

Go to Diagnostic
Aids

Go to Step 12

Go to Step 5

Go to Step 16

Go to Step 7
No
Go to Diagnostic
System Check-
Engine Controls
Go to Step 3
Go to Step 4
Go to Step 6

Go to Step 9