For Self-Diagnostic System and Accessing Trouble Code Memory, see the diagnostic procedures in Section 4. These procedures require an extensive knowledge of electronic fuel injection systems, use extreme care when performing any of these procedures.
The engine controller computer (known as the SMEC, SBEC, SBEC II or PCM) has been programmed to monitor several different circuits of the fuel injection system. This monitoring is called On Board Diagnosis. If a problem is sensed with a monitored circuit, often enough to indicate an actual problem, its fault code is stored in the computer for eventual display to the service technician. If the problem is repaired or ceases to exist, the engine controller cancels the fault code after 50-100 ignition key ON/OFF cycles.
Fault codes are 2 digit numbers that identify which circuit is bad. In most cases, they DO NOT identify which component is bad in a circuit. When a fault code appears it indicates that the engine controller has recognized an abnormal signal in the system. Fault codes indicate the results of a failure but do not always identify the failed component directly.