Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.

Turn ignition off. Loosen and retighten engine ground bolts. See Figure. Disconnect front HO2S harness connector located near oil filler cap. Disconnect ECM harness connector. See Figure. Check continuity of Light Green wire between front HO2S harness connector terminal No. 2 and ECM harness connector terminal No. 50. See Figure. Continuity should exist. Also, check circuit for short to ground and short to voltage. Repair circuit as necessary and retest system. If circuit is okay, go to next step.

CAUTION: DO NOT use ECM ground terminals when measuring voltage.

Reconnect all harness connectors. Start engine and warm to normal operating temperature. Measure voltage between ground and ECM terminal No. 50 (Light Green wire) by backprobing. Increase engine speed to 2000 RPM. The following conditions should exist:
- Voltage cycles from 0-0.3 volt to 0.6-1.0 volt and back more than 5 times within 10 seconds.
- Maximum voltage is more than .6 volt at least once.
- Minimum voltage is less than .3 volt at least once.
- Voltage never exceeds one volt.
If operation is as specified, go to next step. If operation is not as specified, replace front HO2S and retest system.
Turn ignition off. Disconnect 42-pin super multiple junction connector F-12 from firewall. Check continuity between ground and engine control harness connector terminal No. 8A (Black/Red wire). See Figure. Continuity should exist. Also, check circuit for short to voltage. Repair circuit as necessary and retest system. If circuit is okay, go to next step.
No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.