| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. |
Circuit Description
Vapor pressure sensor, canister closed valve Vacuum Switching Valve (VSV) and pressure switching valve VSV are used to detect faults in EVAP system. DTC P0450 is set if 10 seconds after engine starts, vapor pressure sensor fixed value continues for a predetermined amount of time. DTC P0451 is set if vapor pressure sensor output changes while vehicle is standing at idle and pressure switching valve VSV is off. Possible causes are
- Open or short in vapor pressor sensor circuit.
- Faulty vapor pressure sensor.
- Faulty ECM.
Diagnostic Aids
Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.