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Home >> Lexus >> 2000 >> LS 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0120: Throttle Position (TP) Sensor Circuit Malfunction >> Diagnosis & Repair (Using OBD-II Scan Tool)

Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Turn ignition on. Backprobing, measure voltage between terminals No. 2 (Black/Red wire) and No. 18 (Brown wire) and ECM E13 connector. 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.
  2. Turn ignition on. Backprobing, measure voltage between terminals No. 18 (Brown wire) and No. 13 (Pink/Blue wire) at ECM E13 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. 18 (Brown wire) and No. 20 (Black/Blue wire) at ECM E13 connector. Voltage should be 2-2.9 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.
  3. 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 circuit in wiring harness and sensor connector between ECM E13 connector and TP sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
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