Mode III (Stored Codes) Test
READING DIAGNOSTIC CODESThe codes are displayed by the green and red diodes on the Engine Control Module (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.
ECM And A/T Control Unit Location:
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.
Fig. 52 Selecting Modes:
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 Non-Trouble Code Procedures and perform the ECM MAIN POWER AND GROUND CIRCUIT test. Power Supply Testing
Diagnostic Code Display Table:
6. Observe the diodes and note the code(s) displayed.
ERASING DIAGNOSTIC CODES
Diagnostic Trouble Codes can be erased two ways. One way is to disconnect the battery for 24 hours or more. The other is to use the following procedure.
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).
ECM memory is now erased.