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Fault Diagnosis, Main Relay





FAULT DIAGNOSIS, MAIN RELAY

Symptom of fault
The engine fails to start

Diagnostic procedure
1. Connect an ISAT scan tool.

- Ignition switched ON.
- Select the command "MAIN RELAY" in the ISAT menu "ACTIVATE".

Activation of the main relay takes place for 10 seconds at 1 Hz. If a longer activation time is required, the command must be repeated.

- Listen for the sound of the main relay and the [1][2]idle air control valve operating.

Both must click at 1 Hz.

- If only the main relay clicks, continue with step 2.
- If neither the main relay nor the [1][2]idle air control valve clicks, continue with step 5.





2. Check and if necessary replace fuse 16 B.

3. Apply power to the [1][2]idle air control valve.

- Connect a jumper lead between fuses 4 and 16 B.
- If the [1][2]idle air control valve does not click, the fault is located in the lead between fuse 16 B and crimped connection J67.
- If the [1][2]idle air control valve clicks, continue with step 4.





4. Disconnect the main relay.

- Connect a jumper lead between pins 30 and 87 on the relay base.
- If the [1][2]idle air control valve clicks, install a new main relay.
- If the [1][2]idle air control valve does not click, check and if necessary remedy faults in the lead between pin 87 and fuse 16 B and the lead between pin 30 and Batt +.

5. Disconnect the main relay.

- Connect the test lamp in the relay base between pins 85 and 86.
- Ignition switched ON.
- Select MAIN RELAY" again with the ISAT scan tool.
- If the test lamp flashes, install a new main relay.
- If the test lamp does not flash, continue with step 6.





6. Connect the test lamp between the relay base, pin 86 and safe grounding point.

- If the test lamp does not light up, check and if necessary remedy the fault in the lead between pin 86 and Batt +.
- If the test lamp lights up, continue with step 7.

7. Check and if necessary remedy the fault in the lead between pin 85 and pin 31 of the ECM.

- If the lead is OK, continue at "Procedure before replacing ECM".
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