Main Relay (Computer/Fuel System): Testing and Inspection

Checking Main Relay, Steps 1, 2, 3:

1 Connect an ISAT scan tool, contact the SFI system and enter command code 3046.


Check whether the relay is energized at a frequency of 1 Hz (for 10 seconds).


2 With the ignition switched off, connect a break-out box to the ECM. Check the operation of the relay as follows:


Turn the ignition switch to the Drive position and connect a jumper cable between terminals 31 and 24 of the break-out box. Check whether the relay is energized by measuring the voltage at pins 87 and 87B.

If the relay operates, continue with point 6.


If the relay operates but fastens in the energized condition, go to point 5.

If the relay does not work, continue as described below.

3 Check that battery positive voltage is present up to pins 86 and 30 of the relay.

NOTE:
When command code 30XX has been used, the car cannot be started for the following 12 minutes. Use command code FF00 to clear the function, following which the car can be started.

Checking Main Relay, Steps 4 & 5:

4 If battery positive voltage is not present on pins 86 and 30, check the supply cables from the +30 terminal for continuity/shorting to ground.

If the cables are OK, check that the resistance across terminals 85 and 86 of the relay is about 60 ohms.

If it is not, replace the relay.

5 Check the resistance across terminals 30 and 87 and 87B of the relay. When the relay is not energized the resistance should be about 0 ohms and when energized less than 1 ohm.


If the relay is faulty, replace it.

6 If the fault persists in spite of the above checks, the ECM may be faulty. Review "Before Replacing ECM."