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DTC P0120 - Throttle Position (TP) Sensor Circuit Failure

NOTE: For component terminal identification, see TERMINAL IDENTIFICATION  in this article. For wiring diagrams, see WIRING DIAGRAMS article.
  1. If using scan tool, go to step 3). Disconnect TP sensor connector. Using DVOM, check resistance between TP sensor terminals No. 1 and No. 4. If resistance is not 3500-6500 ohms, replace TP sensor. If resistance is as specified, go to next step.
  2. Check resistance between TP sensor terminals No. 2 and No. 4. While monitoring DVOM, slowly open throttle from idle to fully open position. If resistance does not change smoothly, replace TP sensor. If resistance changes smoothly, go to step 4).
  3. Turn ignition switch to ON position. Using scan tool, read TP sensor voltage value. With throttle at idle, value should read 6-20 percent. Value should increase while slowly opening throttle. At wide open throttle, value should read 100 percent. If value is not as specified, replace TP sensor. If value is as specified, go to next step.
  4. Disconnect TP sensor connector. Using DVOM, check continuity between chassis ground and TP sensor connector terminal No. 1 (No. 4 on Diamante). If continuity does not exist, repair wiring harness as necessary. If continuity exists on Stealth and 3000GT, go to next step. On all other models, go to step 6).
  5. Check continuity between chassis ground and TP sensor connector terminal No. 4. If continuity does not exist, repair wiring harness as necessary. If continuity exists, go to next step.
  6. Turn ignition switch to OFF position. Disconnect PCM connector. Ground specified PCM connector terminal. See TP SENSOR-TO-PCM WIRING HARNESS TERMINAL IDENTIFICATION  table. Check for continuity between chassis ground and specified TP sensor connector terminal. If continuity does not exist, repair wiring harness as necessary. If continuity exists on Stealth and 3000GT, go to step 8). On all other models, go to next step.
    TP SENSOR-TO-PCM WIRING HARNESS TERMINAL IDENTIFICATION

    Application TP Sensor Terminal No. PCM Terminal No.
    Diamante 1 81
    2 84
    Stealth & 3000GT 2 84
  7. Reconnect PCM connector. Turn ignition switch to ON position. Check voltage between chassis ground and specified TP sensor connector terminal. See TP SENSOR VOLTAGE CIRCUIT IDENTIFICATION  table. If voltage is not 4.8-5.2 volts, replace PCM. If voltage is as specified, condition required to set DTC is not present at this time. Go to next step.
    TP SENSOR VOLTAGE CIRCUIT IDENTIFICATION

    Application Terminal No.
    Diamante 1
  8. Test is complete. Intermittent problem may exist. Road test vehicle (if necessary) and attempt to duplicate conditions that caused original complaint. Recheck for DTCs. If no DTCs are displayed, go to INTERMITTENT DTCS  .
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