"Intermittent Failures"

Intermittent failures may cause CHECK ENGINE light to flicker or illuminate and go out after the intermittent fault goes away. The corresponding trouble code, however, will be retained in ECU memory. Intermittent failures may be caused by sensor, connector or wiring related problems. See INTERMITTENTS in H - TESTING - W/O CODES article.

When a failure is detected, ECU will start a compensation sequence after 10-20 milliseconds on most circuits. The setting of a fault code will be delayed for approximately 4 seconds. This delay will make diagnosing intermittent problems very difficult.