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Home >> Toyota >> 1997 >> Previa LE, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes >> Circuit Tests >> DTC P0120: Throttle Position (TP) Sensor 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 12 percent with fully closed throttle.
  2. Depress accelerator pedal to floor (WOT). Opening percentage should be approximately 78 percent. If percentages are as specified, check all connections. Problem may be intermittent.
  3. If percentages are not as specified, turn ignition off. Disconnect TP sensor connector. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 4 (Blue/Black 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 article. Replace sensor as necessary. If sensor is okay, go to next step.
  5. Access ECM under driver's seat. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 9 (Brown/Black wire) and No. 10 (Yellow/Red wire) at ECM E6 connector. See Figure. Voltage should be .3-.8 volt with throttle fully closed, and 3.2-4.9 volts with throttle fully open (WOT).
  6. If voltage is as specified, replace ECM and retest. If voltage is not as specified, check for an open or short in Brown/Black or Yellow/Red wire. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary.
  7. Access ECM under driver's seat. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 1 (Blue/Black wire) and No. 9 (Brown/Black wire) at ECM E6 connector. See Figure. If voltage is 4.5-5.5 volts, check wiring harness for an open in Blue/Black wire. If voltage is not 4.5-5.5 volts, replace ECM and retest.
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