Intermittent Failures
Intermittent failures may cause Malfunction Indicator Light (MIL) to flicker or illuminate and go out after the intermittent fault goes away. Intermittent faults will store trouble code(s) in ECM memory until power is disconnected from ECM for at least 20 seconds, with the exception of idle switch failure and ignition faults, which are erased each time ignition switch is turned off. Intermittent failures may be caused by sensor, connector or wiring related problems. See INTERMITTENTS in the TESTS W/O CODES article.
- Ensure Malfunction Indicator Light (MIL) (also known as CHECK ENGINE light) comes on when ignition is on and engine is not running. When engine is started, light should go off. If light remains on while engine is running, a trouble code is present.
- If light does not come on with key on and engine off, check MIL circuit before continuing. See CHART A-1 and CHART A-2 under CODE CHARTS for MIL diagnosis. If light operates and a no start condition exists, see CHART A-3 under CODE CHARTS .
- To retrieve codes, locate monitor coupler connector, near battery. Using a fused jumper wire, connect diagnostic terminal to ground terminal See Fig 1 .
- For example, Code 21 is identified by a flash, flash, pause and flash. See Fig 2 . Each code is displayed 3 times, and then the next code is flashed.
- If engine control system is operating properly (with no faults), a Code 12 should exist with ignition on and engine off. This indicates diagnostic system is capable of storing codes. Ensure engine is in sound mechanical condition.
- Once all codes are displayed, record codes and proceed to SELF-DIAGNOSTIC TROUBLE CODE CHARTS for repair procedure. Remove jumper wire from diagnostic terminal.
- After repairs, erase codes by disconnecting battery cable for 60 seconds. Repeat code retrieval procedure to check for new or returning trouble codes.