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Diagnosis & Repair (Using Lexus 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. 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. Accelerator pedal position sensor voltage should be .5-1.1 volt at VPA circuit and .9-2.3 volts at VPA2 circuit with a fully closed throttle. Depress accelerator pedal to floor (WOT). Accelerator pedal position sensor voltage should be 3.0-4.6 volts at VPA circuit and 3.4-5.0 volts at VPA2 circuit with a fully open throttle. If voltages are within specification, replace ECM and retest. If voltages are not within specification, go to next step.
  2. Access ECM at left front of engine compartment. Turn ignition on. Backprobing connector, measure voltage between terminals No. 35 (Blue/Red wire) and No. 34 (Brown/Yellow wire) at ECM E2 connector. See Figure. Measure voltage between terminals No. 27 (Orange wire) and No. 26 (Brown/White wire) at ECM E2 connector. If voltage reading is 4.5-5.5 volts at both circuits, go to next step. If voltage is not 4.5-5.5 volts at both circuits, replace ECM and retest.
  3. Backprobing connector, measure voltage between terminals No. 33 (Red/Yellow wire) and No. 26 (Brown/White wire) at ECM E2 connector. With fully closed throttle, voltage should be .5-1.1 volt. With Wide Open Throttle (WOT), voltage should be 3.0-4.6 volts. Measure voltage between terminals No. 34 (Brown/Yellow wire) and No. 32 (Red/Black wire) at ECM E2 connector. With fully closed throttle, voltage should be .9-2.3 volts. With WOT, voltage should be 3.4-5.0 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 appropriate SYSTEM & COMPONENT TESTING article. Replace accelerator pedal position sensor as necessary. If accelerator pedal position sensor is okay, check for short or open circuit in wiring harness between ECM E2 connector and accelerator pedal position sensor. See WIRING DIAGRAMS article. Repair wiring as necessary.
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