Self-Diagnosis Function

ECM diagnoses troubles which may occur in the area including the following parts when the ignition switch is ON and the engine 5 running, and indicates the result by turning on or flashing "CHECK ENGINE" light.

- Oxygen sensor
- Water temp. sensor
- Throttle switch (M/T model) or throttle position sensor (A/T model)
- Air temp. sensor
- Pressure sensor
- Ignition signal
- Speed sensor
- EGR system
- CPU (Central Processing Unit) of ECM

ECM and "CHECK ENGINE light operate as follows.

"CHECK ENGINE" light lights when the ignition switch is turned ON (but the engine at stop) with the diagnosis switch terminal ungrounded regardless of the condition of Electronic Fuel Injection system. This is only to check the "CHECK ENGINE" light turns OFF.
- If the above areas of Electronic Fuel Injection system is free from any trouble after the engine start (while engine is running), "CHECK ENGINE" light turns OFF.
- When ECM detects a trouble which has occurred in the above areas, it makes "CHECK ENGINE" light turn ON while the engine is running to warn the driver of such occurrence of trouble and at the same time it stores the trouble area in ECM back-up memory. The memory is kept as it is even if the trouble was only temporary and disappeared immediately. And it is not erased unless the power to ECM is shut off for 60 seconds or longer.)

ECM also indicates trouble area in memory by means of flashing of "CHECK ENGINE" light at the time of inspection (i.e. when diagnosis switch terminal is grounded and ignition switch is turned ON).


NOTE: When a trouble occurs in the above areas except EGR system and disappears soon while the diagnosis switch terminal is ungrounded and the engine is running, "CHECK ENGINE" light lights and remains ON as long as the trouble exists but it turns OFF when the normal condition is restored.
When it is EGR system where a trouble occurs, even if it is only a temporary one and disappears soon, "CHECK ENGINE" light remains ON till the ignition switch is turned OFF.