Clearing Diagnostic Trouble Codes

READING DIAGNOSTIC CODES

The codes are displayed by the green and red diodes on the ECM. Codes are read by the number of times the diodes flash.

For example, if the red diode flashes once and the green diode flashes twice this should be interpreted as code 12. The codes are displayed in numerical order starting with the lowest and ending with the highest.

EXTRACTING DIAGNOSTIC CODES

1. Access the ECM from the floor board in front of the center console and position it for observing the diodes.
2. If the engine does not run, turn the key on and proceed to step #4.
3. Start the engine and warm it to operating temperature then idle.

ECM And A/T Control Unit Location:

4. Turn the diagnostic mode selector on the ECM fully clockwise. When both diodes flash 3 times, immediately turn the selector fully counterclockwise. The ECCS system is now in mode 3.

TECH TIP: Remember to turn the mode selector screw back (counterclockwise) right after you see the diodes flash three times. If you wait too long, the self-diagnostics will have moved on to mode 4.

5. If the diodes do not illuminate, refer to Electrical Component And Circuit Diagnosis and perform the ECU Main Power And Ground Circuit test.

Self-diagnosis Codes Availability Chart:

Self-diagnosis Troubleshooting:

6. Observe the diodes and note the code(s) displayed.

ERASING DIAGNOSTIC CODES

1. Turn the ignition key on.
2. Turn the diagnostic mode selector on the ECM fully clockwise until both diodes flash 4 times then turn the selector fully counterclockwise. The ECCS system is now in mode 4.
3. Turn the ignition key off. This will return the ECCS system to mode #1 (normal operating mode).
ECU memory is now erased.