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Diagnosis & Repair (Using Lexus Scan Tool)

WARNING: This page is about a different car, the 2002 Lexus IS 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 .3-.9 volt at VPA circuit and 1.8-2.7 volts at VPA2 circuit. Depress accelerator pedal to floor (WOT). With throttle fully open, accelerator pedal position sensor voltage should be 3.2-4.8 volts at VPA circuit and 4.7-5.1 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 under protective cover, behind left headlight in engine compartment. Turn ignition on. Backprobing, measure voltage between terminals No. 35 (Blue/Yellow wire) and No. 34 (Brown wire) at ECM E4 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.
  3. Turn ignition on. Backprobing, measure voltage between terminals No. 34 (Brown wire) and No. 33 (Pink/Blue wire) at ECM E4 connector. With fully closed throttle, voltage should be .3-.9 volt. With Wide Open Throttle (WOT), voltage should be 3.2-4.8 volts. Measure voltage between terminals No. 34 (Brown wire) and No. 32 (Blue/White wire) at ECM E4 connector. With fully closed throttle, voltage should be 1.8-2.7 volts. With WOT, voltage should be 4.7-5.1 volts. 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 - GS300, IS300, GS430 & LS430 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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