LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 1999 >> SC 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Emission Systems & Sub-Systems >> Fuel Evaporation System (LS400) >> Vapor Pressure Sensor Circuit
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Vapor Pressure Sensor Circuit

  1. Disconnect vapor pressure sensor Black 3-pin connector. Sensor is mounted on top of EVAP charcoal canister. See Figure. Turn ignition on. Measure voltage between terminals VC (Black/Red wire) and E2 (Brown wire) at vapor pressure sensor connector. 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 behind glove box. Disconnect vapor pressure sensor vacuum hose. Turn ignition on.
  3. Backprobing ECM harness connector, measure voltage between terminals No. 18 (Brown wire) at ECM E13 connector and No. 22 (Black/Blue wire) at ECM E11 connector. See Figure. 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 LEMON Manuals