Diagnosis & Repair (Using Lexus Scan Tool)
WARNING: This page is about a different car, the 2003 Lexus GS 430. However, it is still accessible from the selected car via links, so may be relevant.
- Connect Lexus scan tool to Data Link Connector No. 3 (DLC3). See Figure. Turn ignition on. Turn scan tool on. 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 4.6-5.0 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.
- Access ECM at left front of engine compartment. Turn ignition on. Backprobing, measure voltage between ECM E2 connector terminals VC and ETA. See Fig 1. 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.
- Turn ignition on. Backprobing, measure voltage between terminals VTA and ETA at ECM E2 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 VTA2 and ETA at ECM E2 connector. See Fig 2. Voltage should be 2.0-2.9 volts with throttle fully closed and 4.6-5.0 volts with throttle fully open. If voltage is not as specified, go to next step. If voltage is as specified, replace ECM and retest.
- Check TP sensor operation. See THROTTLE POSITION (TP) SENSOR under SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - GS300, GS430, IS300, LS430 & SC430 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. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary.