Reading and Clearing Diagnostic Trouble Codes

*** UPDATED BY TSB # 9113003, DATED FEBRUARY 1991
There are two different wiring harnesses used on this vehicle. A poor connection at a crimp may be causing the check engine light to come on. Refer to the TSB for further information.

Diagnostic Connector Location:

EXTRACTING TROUBLE CODES
1. Turn the ignition key `OFF'.
2. Connect the voltmeter to the self diagnosis connector as shown in Fig. 1.

Diagnostic Trouble Codes 11 - 22:

Diagnostic Trouble Codes 23 - 43:

3. Turn the ignition key on and note the indication of the voltmeter. If the voltmeter indicates a steady 12 vdc the ECU has failed. If the voltmeter fluctuates, note the position and width of pulses and compare the pattern to the ECU codes chart to determine the error code.
NOTE: There may be more than one error code stored in the ECU memory. If so they will be displayed in ascending order with a 2 second pause between each code.
Also, the oxygen sensor code is erased when the ignition is turned off. To test for oxygen sensor codes drive the vehicle a significant distance and check for diagnostic codes before turning the ignition off.

ERASING TROUBLE CODES
After the cause of a failure code has been detected and corrected the diagnostic code memory of the ECU should be cleared by disconnecting the vehicle battery for 15 seconds or more.