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Home >> Toyota >> 2000 >> Avalon XL >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0120: Throttle Position (TP) Sensor Circuit >> Diagnosis & Repair
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Diagnosis & Repair

  1. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on. Using 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 (WOT). 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 ground and terminal No. 1 (Blue/Red 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 sensor is defective, replace TP sensor. If sensor is okay, go to next step.
  4. Connect TP sensor harness connector. Access ECM behind passenger's side kick panel. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 23 (Green wire) and No. 18 (White wire) at ECM harness connector E5. See Figure. Voltage should be .3-1.0 volt with throttle fully closed, and 2.7-5.2 volts with throttle fully open (WOT). If voltages are as specified, replace ECM. If voltages are not as specified, repair open or short in Green wire between TP sensor and ECM. See WIRING DIAGRAMS article.
  5. Access ECM behind passenger's side kick panel. 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 E5. 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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