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Diagnosis & Repair (Using Lexus Scan Tool)

WARNING: This page is about a different car, the 2002 Lexus GS 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 throttle valve opening percentage at VTA circuit and voltage at VTA2 circuit. Depress accelerator pedal to floor (WOT). Opening percentage should be 64-96 percent and voltage should be 4.6-5.1 volts with a fully open throttle. Release accelerator pedal. Opening percentage should be 8-20 percent and voltage should be 2.0-2.9 volts with a fully closed throttle. If readings are within specification, replace ECM and retest. If readings are not within specification, go to next step.
  2. Access ECM at left front of engine compartment. Turn ignition on. Backprobing, measure voltage between ECM E2 connector terminals No. 23 (Blue/Red wire) and No. 22 (Brown 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 (Brown wire) and No. 25 (Yellow wire) at ECM E4 connector. Voltage should be .4-1.0 volt with throttle fully closed and 3.2-4.8 volts with throttle fully open. Backprobing, measure voltage between terminals No. 22 (Brown wire) and No. 24 (Black wire) at ECM E2 connector. Voltage should be 2.0-2.9 volts with throttle fully closed and 4.6-5.1 volts with throttle fully open. If voltage is not as specified, go to next step. If voltage is as specified, replace ECM and retest.
  4. Check TP sensor operation. See SYSTEM & COMPONENT TESTING - GS300, IS300, GS 430 & LS430 article. Replace TP sensor as necessary. If TP sensor is okay, check for short or open circuits in wiring harness and sensor connector between ECM E2 connector and TP sensor.
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