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Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn ignition on. Backprobing connector, measure voltage between terminals VPTK and EPTK at ECM E5 connector. See Figure. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM and retest system.
    NOTE: DO NOT apply more than 19.7 in. Hg (500mm Hg) of vacuum to vapor pressure sensor.
  2. Backprobing ECM harness connector, measure voltage between terminals EPTK and PTNK at ECM E5 connector. See Figure. Disconnect vacuum supply hose (hose closest to electrical connector) from vapor pressure sensor. Sensor is mounted on charcoal canister and is located next to fuel tank. Connect a vacuum pump to sensor. If voltage is 2.9-3.7 volts without vacuum applied, and .5 volt or less with 1.2 in. Hg (30mm Hg) of vacuum applied, replace ECM and retest system. If voltage is not as specified, go to next step.
  3. Check for an open or short circuit in wiring harness and connectors between vapor pressure sensor and ECM. See Figure and Figure . See VAPOR PRESSURE SENSOR/ECM CONTINUITY CHECK  table. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, replace vapor pressure sensor and retest system.
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