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Home >> Lexus >> 1997 >> ES 300 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0450 - EVAP Pressure Sensor Malfunction >> Diagnosis & Repair

Diagnosis & Repair

  1. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 1 (Yellow wire) and No. 22 (Brown wire) at ECM E9 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.
  2. Backprobing ECM harness connector, measure voltage between terminals No. 13 (Blue/Red wire) at ECM E8 connector and No. 22 (Brown wire) at ECM E9 connector. Disconnect vacuum hose from vapor pressure sensor. Sensor is located next to brake booster. Connect a vacuum pump to sensor. If voltage is 3.0-3.7 volts without vacuum applied and .5 volt with 1.2-19.7 in. Hg (8-135 kPa) vacuum applied, 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 appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor. Retest system.
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