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Home >> Mitsubishi >> 1995 >> Eclipse GS, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 2.0L Turbo >> Diagnostic Tests >> Code P0120: Throttle Position Circuit Fault

Code P0120: Throttle Position Circuit Fault

NOTE: For component terminal identification, see TERMINAL IDENTIFICATION  in this article. For appropriate WIRING DIAGRAMS, see WIRING DIAGRAMS  section.
  1. Using scan tool MUT II mode, read SERVICE DATA No. 26 (closed throttle position switch). Scan tool display should switch between ON (throttle at idle) and OFF (throttle open slightly). If throttle position switch is okay, go to step 5). If throttle position switch is not okay, go to next step.
  2. Disconnect throttle position sensor connector. Check continuity between position sensor terminal No. 3 (Yellow/Red wire) and No. 4 (Black wire). Continuity should exist with throttle at idle. Continuity should not exist when throttle is opened. If continuity is as specified, go to next step. If continuity is not as specified, replace throttle position sensor.
  3. Disconnect throttle position sensor connector. Turn ignition on. Measure voltage between position sensor connector terminal No. 3 (Yellow/Red wire) and ground. Voltage should be 4 volts or more. Check continuity between position sensor connector terminal No. 4 (Black wire) and ground.
  4. If voltage is as specified and continuity exists, check throttle position sensor connector. If throttle position sensor connector is okay, replace PCM. If voltage is not as specified or continuity does not exist, check PCM connector and wiring harness between PCM and throttle position sensor connector. If connector and wiring is okay, replace PCM.
  5. Disconnect throttle position sensor connector. Measure resistance between position sensor terminal No. 1 (Green/Yellow wire) and No. 4 (Black wire). Resistance should be 3.5-6.5 k/ohms. While slowly moving throttle from idle to full open, measure resistance between position sensor terminal No. 2 (Brown/Red wire) and No. 4 (Black wire).
  6. If resistance is not within specification or does not change smoothly with throttle valve position, replace throttle position sensor. If throttle position sensor is okay, go to next step.
  7. Turn ignition on. Measure voltage between position sensor connector terminal No. 1 (Green/Yellow wire) ground. Voltage should be 4.8-5.2 volts. Check continuity between position sensor connector terminal No. 4 (Black wire) and ground. If voltage is within specification and continuity exists, go to next step. If voltage is not within specification or continuity does not exist, go to step  10 .
  8. Connect throttle position sensor connector. Turn ignition on. With PCM connector connected, measure voltage between PCM connector terminal No. 84 (Brown/Red wire) and ground. Voltage should be .3-1.0 volt with throttle at idle and 4.5-5.5 volts with throttle full open.
  9. If voltage is not within specification, check throttle position sensor connector and wiring harness between PCM and throttle position sensor connector. If voltage is within specification, check PCM connector. If PCM connector is okay, replace PCM.
  10. Check PCM connector and wiring harness between PCM and throttle position sensor connector. If connector and wiring is okay, replace PCM.
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