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Home >> Toyota >> 1997 >> Avalon XLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes >> Circuit Tests >> DTC P0120: Throttle Position (TP) Sensor Circuit Malfunction >> Diagnosis & Repair

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 throttle fully closed.
  2. Depress accelerator pedal to floor (WOT). Opening percentage should be approximately 70 percent. If percentages are within specification, 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. 1 (Blue/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 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 behind glove box. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 7 (Black/Yellow wire) and No. 22 (Brown wire) at ECM E7 connector. See Figure. Voltage should be .3-1.0 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 an open or short in Black/Yellow wire between TP sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary.
  7. Access ECM behind glove box. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 1 (Blue/Red wire) and No. 22 (Brown wire) at ECM E7 connector. See Figure. If voltage is 4.5-5.5 volts, check wiring harness for an open in Blue/Red wire between TP sensor and ECM. Repair wiring as necessary. If voltage is not 4.5-5.5 volts, replace ECM and retest.
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