Fault Detection and Trouble Code Memory Function
SELF-DIAGNOSIS FUNCTIONThe electronic control unit monitors the input/output signals at all times. When the ECU detects a problem for a specified time, the electronic control unit memorizes the trouble code, and outputs a signal to the self-diagnostic output terminal.
There are 14 diagnosis codes, including the normal code, that can be read out with a voltmeter or the multi-use tester. The diagnosis codes are memorized even if the ignition key is turned off. The trouble codes will, however, be erased when the battery terminal or the electronic control unit harness is disconnected.
NOTE: If a sensor connector is disconnected with the ignition switch turned on, a diagnosis code will be memorized. To erase any diagnostic codes, disconnect the battery negative terminal (-) for 15 seconds or more, and the ECU memory will be erased.
The 13 diagnostic codes are listed above, and if more than one code is detected, they will be indicated sequentially from the smallest to the largest code number.
**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.