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Diagnosis & Repair (Using OBD-II Scan Tool)

WARNING: This page is about a different car, the 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
  1. Access ECM behind glove box. Turn ignition on. Backprobing, measure voltage between ECM E6 connector terminals No. 26 (Red wire) and No. 28 (Light Green/Black wire), and between terminals No. 27 (Black/Red wire) and No. 29 (Light Green 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, measure voltage between terminals No. 22 (Blue/Yellow wire) and No. 28 (Light Green/Black wire), and terminals No. 23 (White/Red wire) and No. 29 (Light Green wire). See Figure. With fully closed throttle, voltage should be .5-1.1 volt (terminals No. 22 and 28) or .9-2.3 volt (terminals No. 23 and No. 29). With Wide Open Throttle (WOT), voltage should be 3.0-4.6 volts (terminals No. 22 and No. 28) or 3.4-5.0 volt (terminals No. 23 and No. 29). If voltage is not as specified, go to next step. If voltage is as specified, replace ECM and retest.
  3. Check accelerator pedal position sensor operation. See ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - ES300 & RX300 article. Replace accelerator pedal position sensor as necessary. If accelerator pedal position sensor is okay, check for short or open circuit in wiring harness and sensor connector between ECM E6 connector and accelerator pedal position sensor. See WIRING DIAGRAMS article. Repair wiring as necessary.
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