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Home >> Toyota >> 1997 >> T100 Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes - 2.7L >> Circuit Tests >> DTC P0120: Throttle Position (TP) Sensor/Switch Circuit Malfunction >> Diagnosis & Repair
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Diagnosis & Repair

  1. Connect scan tool to DLC No. 3 connector. See Figure. Turn ignition on. Using scan tool, monitor throttle valve opening percentage. Opening percentage should be approximately 10 percent with fully closed throttle.
  2. Depress accelerator pedal to floor (WOT). Opening percentage should be approximately 75 percent. If percentages are within specification, check all connections. Problem may be intermittent.
  3. If percentages are not within specification, turn ignition off. Disconnect TP sensor connector. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 1 (Green/Yellow wire) at TP sensor wiring 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 7).
  4. Check Throttle Position (TP) sensor. See ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS - 2.7L article. Replace sensor as necessary. If sensor is okay, go to next step.
  5. Access ECM behind passenger's side kick panel. Turn ignition on. Backprobe ECM connector. On A/T models, measure voltage between terminals No. 9 (Brown/Black wire) and No. 10 (Yellow wire) at ECM E6 connector. See Figure or Figure. On M/T models, measure voltage between terminals No. 9 (Brown/Black wire) and No. 11 (Yellow wire) at ECM E6 connector. On all models, voltage should be .3-.8 volt with throttle fully closed, and 2.7-5.2 volts with throttle fully open (WOT).
  6. If voltage is as specified, replace ECM and retest. If voltage is not as specified, check for open or short in Yellow wire. See appropriate wiring diagram in WIRING DIAGRAMS - 2.7L article. Repair wiring as necessary.
  7. Access ECM behind passenger's side kick panel. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 1 (Green/Yellow wire) and No. 9 (Brown/Black wire) at ECM E6 connector. See Figure or Figure. If voltage is 4.5-5.5 volts, check wiring harness for open in Green/Yellow wire. If voltage is not 4.5-5.5 volts, replace ECM and retest.
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