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Home >> Lexus >> 2003 >> IS 300 Base, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 39 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0120: Throttle Position (TP) Sensor Circuit Malfunction >> Diagnosis & Repair (Using OBD-II Scan Tool)
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Diagnosis & Repair (Using OBD-II Scan Tool)

WARNING: This page is about a different car, the 2002 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.
  1. Access ECM at left front of engine compartment. Turn ignition on. Backprobing connector, measure voltage between ECM E2 connector terminals No. 22 (Brown wire) and No. 23 (Blue/Red 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.
  2. Turn ignition on. Backprobing connector, measure voltage between terminals No. 22 (Brown wire) and No. 25 (Yellow/Green wire) at ECM E2 connector. See Figure. 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 (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.
  3. Disconnect TP sensor 4-pin connector. Measure resistance between TP sensor 4-pin connector terminal Blue/Red and Brown wires. If resistance is 1.25-2.35 k/ohms, go to next step. If resistance is not 1.25-2.35 k/ohms, replace TP sensor.
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