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Home >> Toyota >> 2003 >> Matrix Base, FWD, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 13 (Engine Control System Self-Diagnostics - V6) >> Diagnostic Tests >> DTC P0120: Throttle Position Sensor Circuit >> Diagnosis & Repair
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Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
  1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on and then turn hand-held tester or scan tool on. Using hand-held tester or scan tool, monitor throttle valve opening percentage. Opening percentage should be approximately 10 percent with fully closed throttle, and 75 percent with fully open throttle. 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. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on. Measure voltage between terminals No. 1 (Blue/Red wire) and No. 2 (White wire) at TP sensor harness connector. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, go to step  5.
  3. Turn ignition off. Check TP sensor. See ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - V6 & V8 article. If TP sensor is okay, go to next step. If TP sensor is defective, replace TP sensor.
  4. Connect TP sensor harness connector. Access ECM behind glove box. See Figure. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 23 (Black/White wire) and No. 18 (White wire) at ECM harness connector E8. See Figure. Voltage should be .3-1.0 volt with throttle fully closed and 3.2-4.9 volts with throttle fully open. If voltages are as specified, replace ECM. If voltages are not as specified, repair open or short in Black/White wire between TP sensor and ECM. See WIRING DIAGRAMS article.
  5. Access ECM behind glove box. See Figure. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (White wire) at ECM harness connector E8. See Figure. If voltage is 4.5-5.5 volts, repair open in Blue/Red wire between TP sensor and ECM. See WIRING DIAGRAMS article. If voltage is not 4.5-5.5 volts, replace ECM.
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