HARD FAILURES
Hard failures cause malfunction light to illuminate and remain on until problem is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, control unit will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, the vehicle runs but driveability will not be optimum.
INTERMITTENT FAILURES
Intermittent failures may cause CHECK ENGINE light to flicker or illuminate and go out after the intermittent fault goes away. However, the corresponding trouble code will be retained in ECU memory. If related fault does not reoccur within a certain time frame, related trouble code will be erased from ECU memory. Intermittent failures may be caused by a sensor, connector or wiring related problems. See INTERMITTENTS in TESTS W/O CODES article.
Scheme 38
- Using jumper wire, ground Green 1-pin connector. Connector is located at back of left front wheelwell. (Scheme 38)
- With ignition on and engine stopped, observe Check Engine or MIL light. Note trouble codes. Check TROUBLE CODE IDENTIFICATION table for possible cause. If light remains on continuously, ECU is defective.
CLEARING CODES
- Disconnect negative battery cable. Depress brake pedal for at least 5 seconds. Reconnect battery cable.
- Ground test connector with jumper wire. Turn ignition on, but do not start engine for 6 seconds.
- Start engine and run at 2000 RPM for 2 minutes. Verify no codes are displayed.
SUMMARY
If no fault codes (or only pass codes) are present, proceed to TESTS W/O CODES for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.).
CODE 14: ATMOSPHERIC PRESSURE SENSOR
Is same code No. present after performing after-repair procedure? If NO, atmospheric pressure sensor is okay. If YES, replace engine control unit.
