Mike's Workshop Manuals: Service manuals for every vehicle
Home >> Lexus >> 2000 >> SC 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Emission Systems & Sub-Systems >> Fuel Evaporation System (GS300 & GS400) >> Vapor Pressure Sensor Circuit

Vapor Pressure Sensor Circuit

  1. Disconnect vapor pressure sensor connector. Sensor is mounted on top of EVAP charcoal canister underneath rear of vehicle and has a Black 3-pin connector. See Figure or Figure . Turn ignition on. Measure voltage between terminals E2 (Brown wire) and VC (Blue/Red wire) at vapor pressure sensor connector terminals. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, check wiring harness between sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM.
  2. Turn ignition off. Reconnect vapor pressure sensor connector. Access ECM harness connectors in left front of engine compartment. Disconnect vapor pressure sensor vacuum hose. Turn ignition on.
  3. On GS300, backprobing ECM harness connector, measure voltage between terminals No. 18 (Blue/Yellow wire) at ECM E5 connector and No. 18 (Brown wire) at ECM E3 connector. See Figure. On GS400, backprobing ECM harness connector, measure voltage between terminals No. 18 (Brown wire) at ECM E3 connector and No. 22 (Blue/Yellow wire) at ECM E5 connector. See Figure. On all models, voltage reading should be as follows:
    • 3.0-3.6 volts with no vacuum applied.
    • 1.3-2.1 volts with .59 in. Hg (2.0 kPa) of vacuum applied.
    • 4.2-4.8 volts with .22 psi (1.5 kPa) of pressure applied.

    If voltage is not as specified, replace vapor pressure sensor.

scientia non olet · About Mike's Workshop Manuals