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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 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 connector, measure voltage between ECM E5 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 connector, measure voltage between terminals No. 22 (Brown wire) and No. 25 (Yellow wire) at ECM E5 connector. Voltage should be .4-1.0 volt with throttle fully closed and 3.2-4.8 volts with throttle fully open. Backprobing connector, measure voltage between terminals No. 22 (Brown wire) and No. 24 (Blue/Black wire) at ECM E5 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 appropriate SYSTEM & COMPONENT TESTING 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 E5 connector and TP sensor.
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