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Diagnosis & Repair (Using Lexus 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. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on. Turn scan tool on. Using Lexus scan tool, monitor accelerator pedal position sensor voltage at VPA and VPA2 circuits. With throttle fully closed, accelerator pedal position sensor voltage should be .5-1.1 volt at VPA circuit and .9-2.3 volts at VPA2 circuit. Depress accelerator pedal to floor (WOT). With throttle fully open, accelerator pedal position sensor voltage should be 3.0-4.6 volts at VPA circuit and 3.4-5.0 volts at VPA2 circuit. If voltages are as specified, replace ECM and retest. If voltages are not as specified, go to next step.
  2. 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 ECM E6 connector 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.
  3. 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.
  4. 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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