LEMON Manuals: Even more car manuals for everyone
Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 204 (Engine Controls - Self-Diagnostics - 1.8L - Ca) >> Diagnostic Tests >> DTC P1491: Vacuum Cut Valve By-Pass Valve >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Nissan Sentra. However, it is still accessible from the selected car via links, so may be relevant.
  1. Remove vacuum cut valve with vacuum cut valve by-pass valve connected. See Figure . Apply vacuum to port "A". See Figure . Vacuum should not exist at port "B". Apply vacuum to port "B". Vacuum should exist at port "A". Blow air in port "B". Air should flow out of port "A" with some resistance. Using jumper wires, apply battery voltage and ground between vacuum cut valve by-pass valve terminals. Air should flow freely through ports "A" and "B" in both directions. If operation is as specified, go to next step. If operation is not as specified, go to step  3 .
  2. Check EVAP purge line between canister and fuel tank for blockage or disconnection. Check EVAP canister. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING article. Check purge port of fuel tank for blockage. If problem exists, repair as necessary and retest system. If problem does not exist, go to step  8 .
  3. Disconnect by-pass hoses between vacuum cut valve and vacuum cut valve by-pass valve. Check hoses for blockage. If problem exists, repair as necessary and retest system. If problem does not exist, go to next step.
  4. Remove vacuum cut valve by-pass valve. Using fused jumper wires, apply battery voltage and ground 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.
  5. Remove vacuum cut valve. See Figure . Plug ports "C" and "D". See Figure . Apply vacuum to port "A". Vacuum should not exist at port "B". Apply vacuum to port "B". Vacuum should exist at port "A". Blow air in port "B". Air should flow out of port "A" with some resistance. Unplug ports "C" and "D". Blow air in port "A". Air should flow freely out of port "C". Blow air in port "B". Air should flow freely out of port "D". If operation is as specified, go to next step. If operation is not as specified, replace vacuum cut valve and retest system.
  6. Turn ignition off. Check vacuum hose connected to EVAP Control System Pressure Sensor (EVAP-CSPS) for damage and blockage. See Figure . If problem exists, repair as necessary and retest system. If problem does not exist, go to next step.
  7. Disconnect EVAP-CSPS harness connector. Inspect connector for water. If water exists, repair or replace connector as necessary. If water does not exist, go to next step.
    8. CAUTION: DO NOT apply more than 5.91 in. Hg of vacuum to EVAP-CSPS. Replace EVAP-CSPS if it has been dropped from a height of more than 20" (.5 m) onto a hard surface such as concrete.
  8. Remove EVAP-CSPS with its harness connector connected. Turn ignition on. Using a hand vacuum pump, apply 2.76 in. Hg of vacuum to EVAP-CSPS. Using a DVOM, backprobe PCM harness connector and measure voltage between ground and terminal No. 84 (Pink wire) at PCM harness connector. See Figure and Figure . Voltage should be .4-.6 volt. Disconnect vacuum pump. Voltage should be 3.0-3.6 volts. If voltage is as specified, go to next step. If voltage is not as specified, replace EVAP-CSPS and retest system.
  9. Check vacuum hose connected to EVAP Canister Vent Control Valve (EVAP-CVCV) for damage and blockage. If problem exists, replace as necessary and retest system. If problem does not exist, go to next step.
  10. Remove EVAP-CVCV. Check EVAP-CVCV for rust and damage. Rust should not exist in port "B". See Figure . If problem exists, replace EVAP-CVCV. If problem does not exist, go to next step.
  11. Using fused jumper wires, apply battery voltage and ground between EVAP-CVCV terminals (component side). See Figure . Air applied to port "A" should not flow from port "B". Remove jumper wires. Air applied to port "A" should now flow from port "B". If EVAP-CVCV operates as specified, go to next step. If EVAP-CVCV does not operate as specified, replace EVAP-CVCV and retest system.
  12. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE  under SELF-DIAGNOSTIC SYSTEM.
scientia non olet · About LEMON Manuals