Main Relay

FAULT DIAGNOSIS, MAIN RELAY

Fault Symptom.
The engine fails to start

DIAGNOSTIC PROCEDURE

1. Checking Main Relay Operation
Connect the Scan Tool.
Ignition switch in the ON position.
Select "ACTIVATE".
Select "MAIN RELAY".
The main relay is activated for 10 seconds at 1 Hz. For longer activation the command must be repeated.
Listen for the sound of the main relay and idle air control (IAC) valve working. Both should click at a frequency of 1 Hz.

If only the main relay clicks, continue with point 2.

If neither the main relay nor the IAC valve clicks, continue with point 4.





2. Applying Current To The IAC Valve
Unplug the ignition discharge module's 10-pin connector.
Connect the test lamp to pins 10 and 6 of the ignition discharge module connector.
The test lamp should light up.

If the test lamp lights up, the fault is located between crimped connections J37 and J67.

If the test lamp does not light up, connect a 12 V/60 W bulb between pin 10 and battery positive.
- If the IAC valve clicks, continue with point 3.
- If the IAC valve does not click, the fault is located between crimped connections J67 and J37.





3. Checking The Main Relay
Remove the main relay.
Connect a jumper lead between pins 30 and 87 on the relay base.
The IAC valve should click.

If the valve clicks, change the main relay.

If the valve does not click, check the lead between pin 87 and crimped connection J37 and the lead between pin 30 and battery positive and take remedial action if necessary.

4. Checking The Main Relay
Remove the main relay.
Connect the test lamp to pins 85 and 86 of the relay base.
Ignition switch in the ON position. Select" MAIN RELAY'.
The test lamp should flash.

If the test lamp flashes, change the main relay.

If the test lamp does not flash, continue with point 6.





5. Checking The Main Relay Voltage Supply
Connect the test lamp to pin 86 of the relay base and a good grounding point.
The test lamp should light up.

If the test lamp lights up, continue with point 6.

If the test lamp does not light up, check the lead between pin 86 and battery positive and take remedial action if necessary.

6. Checking The Main Relay's Connection To Ground
Check the lead between pin 85 and pin 31 of the control module and take remedial action if necessary..

If the lead is OK, refer to Before Replacing A Control Module.

If the lead is not OK, rectify the fault.