Isuzu 4JA1 Workshop Manual page 465

DTC P1625 (Symptom Code B) (Flash Code 76)
Circuit Description
The engine control module (ECM) main relay is
energized when the ECM receives an ignition voltage
switch ON signal. When the ignition switch is OFF, the
ECM main relay is de-energized after a certain length of
time passed. If the ECM detects the ECM main relay
has been ON since the ignition switch was turned OFF,
this DTC will set.
Condition for Running the DTC
• The ignition switch is OFF.
Condition for Setting the DTC
• The ECM detects that the ECM main relay is
turned ON for longer than 2 seconds.
Action Taken When the DTC Sets
• The ECM does not illuminate 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 OFF the ignition for 30 seconds.
3. Monitor the Diagnostic Trouble Code (DTC)
Information with the scan tool.
Does the DTC fail with the ignition switch OFF?
3 1. Disconnect the ECM main relay.
2. Monitor the DTC Information with the scan tool.
Does the DTC fail with the ignition switch OFF?
4 1. Turn OFF the ignition.
2. Disconnect the ECM main relay.
3. Connect a test lamp between the control circuit
of the ECM main relay harness (pin 4 of X-12
connector) and battery voltage.
4. Keep the ignition switch OFF.
Does the test lamp illuminate?
5 1. Test the control circuit of the ECM main relay
between the engine control module (ECM) (pin
56 of C-56 connector) and the ECM main relay
(pin 4 of X-12 connector) for a short to ground.
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
6 Repair the short to battery on the voltage feed
supply circuit to the ECM between the ECM (pin 41
of C-56 connector) and the ECM main relay (pin 1 of
X-12 connector).
Did you complete the repair?
7 Replace the ECM main relay.
Did you complete the replacement?
Action
Engine Control System (4JH1) 6E-211
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.
• Faulty or sticking ECM main relay may set this
DTC.
Test Description
The numbers below refer to the step number on the
diagnostic table.
2. If this DTC is present, scan tool can communicate
with the ECM when the ignition switch is OFF.
DTC P1625 (Symptom Code B) (Flash Code 76)
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 Step 3

Go to Step 6

Go to Step 5

Go to Step 9

Go to Step 9

Go to Step 9
No
Go to Diagnostic
System Check-
Engine Controls
Go to Diagnostic
Aids
Go to Step 4
Go to Step 7
Go to Step 8
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