System Diagnosis

The self-diagnostic capabilities of this system, if properly utilized, can greatly simplify testing. The SMEC has been programmed to monitor several different circuits of the engine control system. If a problem is sensed with a monitored circuit, a fault code is stored in the SMEC.

The check engine light will illuminate and SMEC will enter limp-in mode. In this mode, SMEC attempts to compensate for the failure of a particular component by substituting information from other sources. This will allow vehicle to be operated until proper repairs can be made.

Once these codes are known, refer to FAULT CODES listed in this article to determine the questionable circuit. Test circuits and repair or replace as necessary. If problem is repaired or ceases to exist, the logic module cancels fault codes after 50-100 ignition on/off cycles. If DRB-II is being used, refer to CLEARING CODES in this article.

The setting of a specific fault code is the result of a particular system failure, NOT the reason for that failure, such as failure of a specific component. The existence of a particular code denotes the probable area of the malfunction, not necessarily the failed component itself.