Clearing Diagnostic Trouble Codes

Fig. 69 Trouble Code Example:

READING DIAGNOSTIC CODES
The stored malfunction codes are accessed using the red diode on the ECM. The codes are interpreted by the number and duration the diode flashes.

A long flash (0.6 seconds) indicates the "tens" digit while a short flash (0.3 seconds) is the "ones" digit. All flashes will have a short pause in between.

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

If more than one code is in memory the ECM will always display the lowest number first, pause for about two seconds and then go the next higher number. This will continue until all the stored codes have been displayed. The ECM will then go back to the lowest numbered code and repeat the cycle.

Fig. 35 Selecting Modes:

EXTRACTING DIAGNOSTIC CODES
1. Access the ECM and position it for observing the diode.
2. Turn the ignition switch on (do not start the engine).
3. Confirm that the "CHECK ENGINE" lamp in the instrument panel illuminates.
If not, check the bulb and/or the bulb circuit. Repair as necessary.
4. Turn the diagnostic mode selector on the ECM fully clockwise for at least two seconds then turn the selector fully counterclockwise. The ECCS system is now in mode 2.
5. Observe the diode and note the code(s) displayed.
NOTE: Code 55 indicates all systems are OK.

Trouble Code ID:

^ Refer to the chart above for code identification and proceed to Diagnostic Charts for trouble code diagnosis.

ERASING DIAGNOSTIC CODES
1. Turn the ignition key on.
2. Turn the diagnostic mode selector on the ECM fully clockwise and wait more than two seconds then turn the selector fully counterclockwise. The ECCS system is now in mode 2.
3. Turn the diagnostic mode selector on the ECM fully clockwise and wait more than two seconds then turn the selector fully counterclockwise. The ECCS system is now in mode 1.
ECM memory is now erased.