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

Checking the Main Relay

Tools:
- Breakout Box 86 11 006
- Test cables 8611352


1 Unplug the LH control module and mass air flow sensor connectors. Connect Breakout Box 8611 006.




2 Ground pin 21.

3 Check that battery voltage is present at:
- Control module connector pin 9
- Mass air flow sensor
pin 2 (-M1987 fuel injection engine, - M1988 turbo engine)
pin 5 (M1988- fuel injection engine, M1989- turbo engine)

If voltage is present at these points the main relay and appurtenant leads are OK.

If it is not, continue checking as described below.

4 Remove the glove box and withdraw the relay panel.




5 Check that battery voltage is present on relay terminals 30 and 86.

If it is not, check that the lead to the positive terminal block is OK.

6 Ground terminal 85 and check that battery voltage is present on terminals 87 and 87B.

If it is, continue as described in point 7.

If it is not, change the main relay.

7 Check the lead from relay terminal 85 to LH control module pin 21 and the lead from relay terminal 87 to fuel pump relay terminal 86 (via the pressure switch, LH 2.2 turbo engine) and the lead from relay terminal 87B to the mass air flow sensor's:
pin 2 (-M1987 fuel injection engine, -M1988 turbo engine)
pin 5 (M1988- fuel injection engine, M1989- turbo engine)