Circuit Description

WARNING: This page is about a different car, the 2002 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.

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.