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Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.
  1. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 2 (Yellow/Black wire) and No. 18 (Brown wire) at ECM E8 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 (66.7 kPa) to vapor pressure sensor.
  2. Locate vapor pressure sensor on top of fuel tank. See Figure. Leaving harness connector attached, remove vapor pressure sensor from top of fuel tank. See Figure. Backprobing ECM harness connectors, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E5 connector and terminal No. 18 (Brown wire) at ECM E8 connector. See Figure. Connect a vacuum pump to vapor port on sensor. Voltage should be 2.9-3.7 volts without vacuum applied, and .5 volts or less with 1.18 in. Hg (4.0 kPa) applied. If voltage is as specified, replace ECM and retest system. If voltage is not as specified, go to next step.
  3. Check for an open or short in wiring harness between vapor pressure sensor and ECM. See WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor.
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