Circuit Description

WARNING: This page is about a different car, the 2002 Lexus RX 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 P0441 or P0446 is set if EVAP system leak is detected by ECM or if there is a malfunction in EVAP VSV, pressure switching valve VSV, or in vapor pressure sensor. Possible causes are:

Disconnected, cracked, damaged or blocked vacuum hose.
Fuel tank cap installed incorrectly.
Damaged fuel tank cap.
Open or short circuit in vapor pressure sensor circuit.
Faulty vapor pressure sensor.
Open or short in EVAP VSV circuit.
Faulty EVAP VSV.
Open or short in canister closed valve VSV circuit.
Faulty canister closed valve VSV.
Open or short in pressure switching valve VSV circuit.
Faulty pressure switching valve VSV.
Damaged fuel tank.
Faulty charcoal canister.
Damaged fuel tank overfill check valve.
Faulty ECM.

NOTE: If DTC P0441, DTC P0446, DTC P0450 or DTC P0451 is output after DTC P0440, perform appropriate diagnostic test first before performing DTC P0440 diagnostic test.