Vapor Pressure Sensor

WARNING: This page is about a different car, the 2003 Lexus GX 470. However, it is still accessible from the selected car via links, so may be relevant.

Turn ignition on. Using voltmeter, measure voltage between terminals VC and E2 on wiring harness side of ECM. See Fig 1. Power source voltage should be 4.5-5.5 volts.
To test vapor pressure sensor output voltage, remove fuel tank cap. Connect voltmeter to terminals PTNK and E2 on wiring harness side of ECM and measure output voltage. See Fig 2. Voltage should be 3-3.6 volts. If not, repair or replace as necessary.

Fig 1: Inspecting Vapor Pressure Sensor Power Source Voltage

Fig 2: Inspecting Vapor Pressure Sensor Power Output Voltage