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Diagnosis & Repair (Using OBD-II Scan Tool)

WARNING: This page is about a different car, the 2000 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.
  1. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (Brown/White wire) at ECM harness connector E7. 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.
  2. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown/White wire) and No. 13 (Red/Yellow wire) at ECM harness connector E7. With fully closed throttle, voltage should be .4-1.0 volt. With fully open throttle, voltage should be 3.2-4.8 volts. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Brown/White wire) and No. 20 (Yellow/Black wire) at ECM harness connector E7. With fully closed throttle, voltage should be 2.0-2.9 volts. With fully open throttle, voltage should be 4.7-5.1 volts. If voltage readings are as specified, replace ECM. If voltage readings are not as specified, go to next step.
  3. Check Throttle Position (TP) sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace TP sensor. If problem does not exist, check for an open or short in wiring between ECM and TP sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring harness as necessary.
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