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Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 41 (Engine Controls - Self-Diagnostics - Quest) >> Diagnostic Tests >> DTC P1490: Vacuum Cut Valve By-Pass Valve >> Diagnostic Procedure

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.
  1. Turn ignition off. Disconnect vacuum cut valve by-pass valve harness connector. See Figure. Turn ignition on. Measure voltage between ground and vacuum cut valve by-pass valve harness connector terminal No. 2 (Blue/Yellow wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit and retest system. See WIRING DIAGRAMS article.
  2. Turn ignition off. Disconnect ECM harness connector. See Figure. Check continuity of Blue/Green wire between vacuum cut valve by-pass valve harness connector terminal No. 1 and ECM harness connector terminal No. 120. See Figure. 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.
  3. Remove vacuum cut valve by-pass valve. Using fused jumper wires, apply battery voltage between vacuum cut valve by-pass valve terminals. See Figure. Air should flow between ports "A" and "B". Remove jumper wires. Air should not flow between ports "A" and "B". If vacuum cut valve by-pass valve operates as specified, go to next step. If vacuum cut valve by-pass valve does not operate as specified, replace vacuum cut valve by-pass valve and retest system.
  4. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
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