Main Relay Test

Symptom Of Fault.
Engine will not start.





Diagnostic Procedure.
1. Check the operation of the main relay
- Connect an ISAT scan tool.
- Ignition switch in ON position.
- Select "ACTIVATE".
- Select "MAIN RELAY".
The main relay is activated for 10 seconds at a frequency of 1 Hz. If a longer activation time is required, the command will have to be repeated.
- Listen for the sound of the main relay and idle air control valve working.
They should both click at a frequency of 1 Hz (once a second).

Does only the main relay click?
YES:
^ Continue with point 2.
NO:
^ Neither the main relay nor the idle air control valve clicks. Continue with point 4.





2. Forcibly supply the main relay with power
- Unplug the ignition discharge module's 10-pin connector.
- Connect a 12 V, 60 W bulb to pin 10 and battery positive (B+).

Does the idle air control valve click?
YES:
^ Continue with point 3.
NO
^ The fault is in the lead between crimped connections J37 and J67.





3. Check the main relay
- Remove the main relay.
- Connect a jumper lead between pins 30 and 87 on the relay holder.

Does the idle air control valve click?
YES:
^ Change the main relay.
NO:
^ Check the lead between pin 87 and crimped connection J37 and the lead between pin 30 and battery positive (B+). Repair or replace the leads it necessary.

4. Check the main relay
- Remove the main relay.
- Connect the test lamp to pins 85 and 86 of the relay holder.
- Ignition switch in ON position.
- Select "ACTIVATE".
- Select "MAIN RELAY".

Does the test lamp flash?
YES:
^ Change the main relay.
NO:
^ Proceed to point 5.





5. Check the main relay's power supply
- Connect the test lamp to pin 86 of the relay holder and a good grounding point.

Is the test lamp on?
YES:
^ Continue. with point 6.
NO:
^ Check the lead between pin 86 and battery positive (B+). Repair or replace it if necessary.

6. Check the main relay's connection to ground
- Check and if necessary repair or replace the lead between pin 85 of the relay holder and pin 31 of the control module.

Is the lead OK?
YES:
^ Proceed at "Before Replacing a Control Module". Component Tests and General Diagnostics
NO:
^ Rectify the fault.