Reading Diagnostic Trouble Codes
Displaying Fault Codes [California (Digifant II)]On Board Diagnosis System
1988 and 1989 vehicles for California equipped with the Digifant II Engine Management System have a permanent, eraseable fault memory in the E.C.U. for self-diagnosis.
NOTE: The Control unit used on Federal Vehicles does not have OBD capabilities and, consequently, does not store diagnostic trouble codes (DTC's).
This memory constantly monitors the Engine Management System and stores any faults that could cause the vehicle to fail an exhaust emissions inspection.
Such faults can ONLY be determined (and stored) by driving the vehicle a minimum of 10 minutes.
An indicator light labeled CHECK is located in a rocker switch on the instrument panel. Each time the engine is started, the indicator light will flash once to inform the operator that the bulb is working.
The light will come on and stay on if a fault develops that could cause the vehicle to fail an exhaust emissions inspection. The light is also used to display a diagnosis code to help the technician repair a problem in the system.
Diagnostic Codes
A diagnostic code consists of four groups of flashes of the indicator light. Each group has a maximum of four flashes. There is a 2.5 second pause (light OFF) between each group of flashes.
The indicator light will come on for two and a half seconds prior to displaying a fault code when the diagnosis procedure is activated. The fault code will continue repeating while the ignition is on.
To continue to next fault code, depress the rocker switch for at least four seconds.
If the fault is not repaired, the indicator light will come on and stay on when the ignition is switched back on to signify that the fault still exists.
The following is an example of the fault code 2342.
Diagnosis Procedure
If a fault is detected and stored in the E.C.U., the fault lamp will light after one minute.
NOTE: The On-Board Diagnostic System may be disabled. Refer to "Notes Regarding ODB System Modifications". Notes Regarding OBD System Modifications
To activate the diagnostic procedure,
- Switch the ignition ON but do not start the engine.
- Press and hold down the rocker switch for longer than four seconds then release.
- The fault indicator lamp will begin flashing diagnosis code.
- Press and hold down the rocker switch again for longer than four seconds then release.
- The indicator lamp will flash the next diagnostic code (if any.)
Note: Do not press the rocker switch during the warning light pauses or the E.C.U. will not switch to the next memorized code.
When all the diagnostic codes have been displayed, the indicator lamp will flash its "End of Fault Sequence" code.
This is a series of 2.5 second flashes ON and 2.5 seconds OFF.
If there are NO faults stored in the E.C.U. memory, the indicator lamp will flash code 4444
For a complete listing of all possible diagnostic codes, see the table on page 57.
CAUTION: Check the wiring and components before making any repairs when a fault code is displayed. This is a sensitive system that may occasionally sense temporary deviations In the air/fuel mixture that are inherent in the normal operation of every vehicle. If a fault code is displayed but no apparent malfunction exists with the indicated component or wiring, check Group 24 of your Technical Information Book for additional information.
The system has a permanent memory and must be cleared after a fault has been repaired. To cancel the memory, the following sequence must be followed.
- The ignition must be OFF.
- Depress the rocker switch and hold.
- Turn the ignition ON and keep the rocker switch depressed for at least tour (4) seconds and then release.
Switch OFF ignition
If no faults exist, the memory will be cleared.
Calif. Only:
The code 0000 is displayed by the indicator light coming on for 2.5 seconds and going off for 2.5 seconds repeatedly.