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Home >> Toyota >> 2000 >> 4Runner Base, RWD, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 4-Cylinder >> 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 should be approximately 75 percent with throttle fully open (WOT). If percentages are as specified, problem is intermittent. Check component and ECM connections. If percentages are not as specified, go to next step.
  2. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 2 (Green/Yellow 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. Check TP sensor. See ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace TP sensor. If problem does not exist, go to next step.
  4. Access ECM behind glove box. Connect TP sensor harness connector. Turn ignition on. Using DVOM, backprobe ECM harness connector. On models with California emissions, measure voltage between terminals No. 9 (Yellow wire) and No. 18 (Blue/Black) at ECM harness connector E6. See Figure. On models without California emissions, measure voltage between terminals No. 9 (Blue/Black wire) and No. 10 (Yellow wire) at ECM harness connector E6. See Figure. On all models, voltage should be .3-.8 volt with throttle fully closed, and 3.2-4.9 volts with throttle fully open (WOT). If voltages are as specified, replace ECM. If voltages are not as specified, repair open or short in wiring between TP sensor and ECM. See WIRING DIAGRAMS article.
  5. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector. On models with California emissions, measure voltage between terminals No. 2 (Green/Yellow wire) and No. 18 (Blue/Black wire) at ECM harness connector E6. See Figure. On models without California emissions, measure voltage between terminals No. 1 (Green/Yellow wire) and No. 9 (Blue/Black wire) at ECM harness connector E6. See Figure. If voltage is 4.5-5.5 volts, repair open in Green/Yellow wire between TP sensor and ECM. If voltage is not 4.5-5.5 volts, replace ECM.
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