Fault Code Display Failure

If the on-board diagnostic system fails to operate, as described under ``Diagnostic Fault Code Output,'' check the following items using a suitable digital volt/ohmmeter and referring to Fig. 3 terminal identification.

Fig. 3 Bosch Motronic Electronic Engine Control System Terminal Identification:

1. Ensure check engine lamp is operational.
2. Ensure special tester or toggle switch and diagnostic plug connections are proper.
3. Locate ECU behind passenger side of instrument panel, then disconnect 35 pin connector from ECU.
4. Check continuity exist between ECU terminal 4 and diagnostic connector terminal 1, ECU terminal 12 and diagnostic connector terminal 2 and ECU terminal 17 and the check engine lamp.
5. Check battery voltage is present at the following:
a. Between main relay terminal 87 and check engine lamp.
b. At ECU terminal 18.
c. Between ECU terminals 5 and 35. Turn ignition switch to Run position, probe ECU terminal 35 with voltmeter positive lead and terminal 5 with negative lead.
6. If all wires and connections test good, replace ECU, then rerun procedure described under ``Diagnostic Fault Code Output.''