| CAUTION | If ECM replacement is instructed in following tests, always ensure ECM connectors and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. |
Note. If DTCs 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 and canister closed valve Vacuum Switching Valve (VSV) are used to detect abnormalities in the 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 tank cap has been left off or not completely tightened recently. This may cause DTC to be set. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected. When ENGINE RUN TIME in freeze frame data is less than 200 seconds, check EVAP VSV, charcoal canister and vapor pressure sensor.