| CAUTION | If ECM replacement is instructed in following tests, always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. |
Note. If DTC P0441, P0446, P0450 or P0451 is output after DTC P0440, perform appropriate test first before performing DTC P0440 test.
Note. For component location, see appropriate illustration in THEORY & OPERATION article.
Circuit Description
Vapor pressure sensor, vapor pressure sensor Vacuum Switching Valve (VSV), canister closed valve VSV and pressure switching valve VSV are used to detect faults in EVAP system. DTC is set if EVAP system leak is detected or vapor pressure sensor malfunctions. Possible causes are
- Damaged, disconnected or blocked vacuum hose(s).
- Fuel tank cap is installed incorrectly.
- Defective fuel tank cap.
- Damaged fuel tank.
- Defective charcoal canister.
- Vapor pressure sensor circuit is open or shorted.
- Defective vapor pressure sensor.
- Defective fuel tank overfill valve.
- Defective ECM.
Diagnostic Aids
Ask customer if fuel cap has been left off or not completely tighten recently. This may cause DTC to be set. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.