| 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 - IMPORT article in GENERAL INFORMATION. |
Note. Vapor canister and some related components can be accessed through trunk by removing trunk floor mat and protective access cover at front of trunk. For component location, see appropriate illustration in THEORY & OPERATION article.
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. ECM determines if a fault is present in EVAP system based on vapor pressure signal circuit. DTC P0440 is set if EVAP system leak is detected in EVAP system components between fuel tank and charcoal canister or vapor pressure sensor malfunctions. Possible causes are
- Hose between fuel tank and charcoal canister damaged.
- Fuel tank cap installed incorrectly.
- Fuel tank cap defective.
- Damaged, disconnected or blocked vacuum hose.
- Fuel tank damaged.
- Charcoal canister damaged.
- Open or short in vapor pressure sensor circuit.
- Faulty vapor pressure sensor.
- Fuel tank overfill check valve damaged.
- Faulty ECM.
Note. If DTC P0441, DTC P0446, DTC P0450 or DTC P0451 is output after DTC P0440, perform appropriate circuit test first before performing DTC P0440 test.
Diagnostic Aids
Ask customer if fuel cap has been left off or not completely tightened recently. This may cause DTC to be set. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.