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Diagnosis & Repair (Using OBD-II Scan Tool)

WARNING: This page is about a different car, the 2002 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.
  1. Access ECM at left front of engine compartment. Turn ignition on. Backprobing connector, measure voltage between ECM E5 connector terminals No. 22 (Brown wire) and No. 23 (Blue/Red wire). 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.
  2. Turn ignition on. Backprobing connector, measure voltage between terminals No. 22 (Brown wire) and No. 25 (Yellow wire) at ECM E5 connector. Voltage should be .4-1.0 volt with throttle fully closed and 3.2-4.8 volts with throttle fully open. Backprobing connector, measure voltage between terminals No. 22 (Brown wire) and No. 24 (Blue/Black wire) at ECM E5 connector. Voltage should be 2.0-2.9 volts with throttle fully closed and 4.6-5.1 volts with throttle fully open. If voltage is not as specified, go to next step. If voltage is as specified, replace ECM and retest.
  3. Check TP sensor operation. See appropriate SYSTEM & COMPONENT TESTING article. Replace TP sensor as necessary. If TP sensor is okay, check for short or open circuit in wiring harness and sensor connector between ECM E5 connector and TP sensor. See WIRING DIAGRAMS article. Repair as necessary.
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