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Home >> Toyota >> 1996 >> Paseo Automatic >> 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 tester to DLC3 connector. See Figure. Turn ignition on. Turn on scan tester. 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 70 percent. If percentages are within specification, inspect 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. 4 (Light Green Red 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 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 behind glove box. Turn ignition on. Backprobe ECM connector. On A/T models, measure voltage between terminals No. 9 (Brown wire) and No. 11 (Yellow/Green wire) at ECM E6 connector. On M/T models, measure voltage between terminals No. 16 (Brown wire) and No. 17 (Yellow/Green wire) at ECM E4 connector. 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).
  6. If voltage is as specified, replace ECM and retest. If voltage is not as specified, check for an open or short in wiring harness between TP sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
  7. Access ECM behind glove box. Turn ignition on. Backprobe ECM connector. On A/T models, measure voltage between terminals No. 1 (Light Green/Red wire) and No. 9 (Brown wire) at ECM E6 connector. On M/T models, measure voltage between terminals No. 16 (Brown wire) and No. 18 (Light Green/Red wire) at ECM E4 connector. See Figure.
  8. On all models, if voltage is 4.5-5.5 volts, check wiring harness for an open in Light Green/Red wire. If voltage is not 4.5-5.5 volts, replace ECM and retest.
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