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Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
  1. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on. On scan tool, select THROTTLE POS and THROTTLE POS #2 in DATA LIST and read value displayed. With accelerator pedal released, throttle valve opening position expressed as percentage (VTA1) should be 8-20 percent, with voltage (VTA2) of 2.0-2.0. With throttle depressed, throttle valve opening position expressed as percentage (VTA1) should be 64-96 percent, with voltage (VTA2) of 4.6-5.0. If percentages are not as specified, go to next step. If percentages are as specified, problem may be intermittent. Check component and ECM connections.
  2. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Yellow wire) and No. 28 (Brown wire) at ECM harness connector E10. 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.
  3. Measure voltage between ECM harness connector E10 terminals No. 21 (Light Green wire) and No. 28 (Brown wire). See Figure. With accelerator pedal released, voltage should be .4-1.0 volts. With accelerator pedal depressed, voltage should be 3.2-4.8 volts. Measure voltage between ECM harness connector E10 terminals No. 31 (Black/Red wire) and No. 28 (Brown wire). With accelerator pedal released, voltage should be 2.0-2.9 volts. With accelerator pedal depressed, voltage should be 4.6-5.0 volts. If voltages are to specification, go to next step. If voltages are not to specification, replace ECM.
  4. Disconnect TP sensor 4-pin harness connector. Measure resistance between connector terminals No. 1 and 2. If resistance is 1.2-3.2 k/ohms at 68°F (20°C), go to next step. If resistance is not to specification, replace TP sensor.
    5. NOTE: During next step, If throttle position is 100 percent, Brown wire is open. If throttle position is zero percent when depressing accelerator pedal, Yellow or Light Green wire is open. If throttle position is not zero percent when releasing accelerator pedal or throttle position is not 100 percent when depressing throttle pedal, Black/Red wire is open or shorted.
  5. Disconnect TP sensor connector and ECM E10 connector. Read throttle opening angle on hand-held tester. With accelerator pedal released, opening percentage should be zero percent. With accelerator pedal depressed, opening percentage should be 64-96 percent. If percentages are not to specification, repair or replace harness and connector. If percentages are to specification, check and replace ECM.
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