Isuzu N 2008 Series Workshop Manual page 189

1A-186 Engine Control System (4JJ1)
Step
Observe the DTC Information with a scan tool.
14
Are there any DTCs that you have not diagnosed?
Circuit/ System Testing DTC P0502 (Model with ABS)
Step
Did you perform the Diagnostic System Check -
1 Engine Controls?
1. Install a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
2
4. Monitor the DTC Information with a scan tool.
Does the DTC fail this ignition?
Attempt to communicate with the EHCU (ABS
module) via the ABS Data table.
3
Does the scan tool communicate with the EHCU?
Monitor the ABS DTC information with a scan tool.
4
Does the ABS DTCs fail the ignition?
1. Turn OFF the ignition.
2. Disconnect the EHCU harness connector.
3. Turn ON the ignition, with the engine OFF.
5
4. Connect a test lamp between the vehicle
speed signal circuit (pin 14 of J22) and a
battery voltage.
Does the test lamp illuminate?
1. Leave the test lamp connected between the
EHCU harness connector and battery voltage.
2. Turn OFF the ignition for 30 seconds.
6
3. Turn ON the ignition, with the engine OFF.
4. Monitor the DTC Information with a scan tool.
Is DTC P0503 set?
1. Test the vehicle speed signal circuit between
the ECM (pin 19 of J14) and the EHCU (pin 14
of J22) for a short to ground.
7
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
1. Test the vehicle speed signal circuit between
the ECM (pin 19 of J14) and the EHCU (pin 14
of J22) for an open circuit or high resistance.
8
2. Repair the circuit(s) as necessary.
Did you find and correct the condition?
1. Inspect for an intermittent and for a poor
connection at the harness connector of the
EHCU (pins 14 of J22).
9
2. Repair the connection(s) as necessary.
Did you find and correct the condition?
Action
Action
Value(s) Yes
—
Go to DTC List
Value(s) Yes
—
Go to Step 2
—
Go to Step 3
—
Go to Step 4
Go to Applicable
— DTC for ABS
Section
—
Go to Step 7
—
Go to Step 9
—
Go to Step 13
—
Go to Step 13
—
Go to Step 13
No
System OK
No
Go to Diagnostic
System Check -
Engine Controls
Go to Diagnostic
Aids
Go to Diagnostic
System Check -
ABS Controls in
Section 4C1 ABS/
ASR
Go to Step 5
Go to Step 6
Go to Step 8
Go to Step 12
Go to Step 10
Go to Step 11