Possible causes

– Faulty Evaporative Emission System (EVAP) Vapor Pressure Sensor
– Evaporative Emission System (EVAP) Vapor Pressure Sensor harness is open or shorted
– Evaporative Emission System (EVAP) Vapor Pressure Sensor circuit poor electrical connection
– Faulty Engine Control Module (ECM)

Tech notes

There is factory service bulletin for the following Toyota models:

2003-2004 Toyota 4Runner
2003-2004 Toyota Tundra
2004 Toyota Camry
2004 Sienna
2004 Highlander
2004 Solara
Toyota Factory Service Bulletin OBDII Code P0451

When is the code detected?

An out of range voltage from the sensor is sent to Engine Control Module (ECM).

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0451 TOYOTA Description

The Evaporative Emission System (EVAP) vapor pressure sensor, VSV for canister closed valve (CCV) and VSV for pressure switching valve are used to detect abnormalities in the evaporative emission control system. The Engine Control Module (ECM) decides whether there is an abnormality in the evaporative emission control system based on the vapor pressure sensor signal.

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TOYOTA Technical Service Bulletins for P0451 code