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Home › Infiniti › 2001 › Q45 Base › Repair and Diagnosis › Engine Performance › System › Engine Controls - Self-Diagnostics › Diagnostic Tests › DTC P0120: Throttle Position (TP) Sensor › Procedure"B"

DTC P0120: Throttle Position (TP) Sensor: Procedure"B"

  1. Turn ignition off. Loosen and retighten 2 engine ground bolts. See Figure. Disconnect TP sensor harness connector. See Figure. Turn ignition on. Measure voltage between ground and TP sensor harness connector terminal No. 4 (Brown/White wire). If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, repair open or short in Brown/White wire between ECM and TP sensor. Retest system.
  2. Turn ignition off. Check continuity between engine ground and TP sensor harness connector terminal No. 2 (Black wire). Also, check circuit for short to voltage. See WIRING DIAGRAMS article. Repair circuit as necessary and retest system. If ground circuit is okay, go to next step.
  3. Disconnect ECM harness connector. See Figure. Check continuity of Green wire between ECM harness connector terminal No. 63 and TP sensor harness connector terminal No. 1. See Figure. Also, check circuit for short to ground and short to voltage. Repair circuit as necessary and retest system. If circuit is okay, go to next step.
    4. CAUTION: DO NOT use ECM ground terminals when measuring voltage.
  4. Reconnect all harness connectors. Start engine and warm to normal operating temperature. Remove vacuum hose from throttle opener. Using a hand vacuum pump, apply vacuum to throttle opener until throttle drum no longer contacts throttle opener rod. Turn ignition on. Measure voltage between ground and ECM terminal No. 63 by backprobing, with throttle in specified positions. See Figure. See THROTTLE POSITION (TP) SENSOR VOLTAGE  table. If voltage is as specified, go to next step. If voltage is not as specified, adjust TP sensor, if possible. See ON-VEHICLE ADJUSTMENTS article. If TP sensor cannot be adjusted, replace TP sensor and retest system.
    5. CAUTION: DO NOT use ECM ground terminals when measuring voltage.
  5. Reconnect all harness connectors. Start engine and warm to normal operating temperature. Measure voltage between ground and ECM terminal No. 65 by backprobing, with engine at specified speeds. See MAF SENSOR VOLTAGE  table. If voltage is as specified, go to step  7. If voltage is not as specified, go to next step.
  6. Disconnect and reconnect MAF sensor harness connector and repeat test. If voltage is still not as specified, remove MAF sensor and check hot film for damage or dust. Repair or replace MAF sensor, if necessary and retest system. If voltage is now as specified, go to next step.
    7. CAUTION: DO NOT use ECM ground terminals when measuring voltage.
  7. Reconnect all harness connectors. Ensure engine is at normal operating temperature. Measure voltage between ground and ECM terminals No. 55, 58 and 59 (CMP sensor signal) by backprobing, with engine at specified speeds. See PIN VOLTAGE CHARTS article. If voltage and waveforms are as specified, go to next step. If voltage or waveforms are not as specified, replace CMP sensor and retest system.
  8. Turn ignition off. Disconnect each fuel injector harness connector. Measure resistance between injector terminals. If resistance is 10-14 ohms at 77°F (25°C) on all injectors, go to next step. If resistance is not 10-14 ohms at 77°F (25°C), replace defective injector and retest system.
  9. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
MAF SENSOR VOLTAGE

Condition Volts
Key On, Engine Off Less Than 1.0
Engine Idling 1.0-1.7
2500 RPM About 2.1
Idle To 4000 RPM (1) 1.0-1.7 To About 4.0
(1) Voltage should increase in proportion to engine speed.
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