Possible Causes
WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.
ECM illuminates MIL and sets DTC P1491 when vacuum cut valve by-pass valve does not operate properly. Possible causes are:
- Defective vacuum cut valve by-pass valve.
- Defective vacuum cut valve.
- Blockage in by-pass hoses.
- Fault in EVAP Control System Pressure Sensor (EVAP-CSPS) or circuit.
- Defective EVAP Canister Vent Control Valve (EVAP-CVCV).
- Blockage in hose between fuel tank and vacuum cut valve.
- Blockage in hose between EVAP canister and vacuum cut valve.
- Defective EVAP canister.
- Blockage in fuel tank purge port.