DTC P0120: Throttle Position (TP) Sensor: Procedure
- If malfunction "A" or "B" was duplicated, go to next step. If malfunction "C" was duplicated, check ignition timing, closed throttle position switch adjustment and target idle speed. See ON-VEHICLE ADJUSTMENTS article. Adjust as necessary. Inspect air intake duct and vacuum hoses for leaks. Repair as necessary and retest system. If no leaks are found, go to next step.
- Turn ignition off. Loosen and retighten 2 engine ground bolts located near oil filler cap. Disconnect TP sensor harness connector. See Fig 1. Turn ignition on. Measure voltage between TP sensor harness connector Red wire and ground. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, repair open or short in Red wire between ECM and TP sensor and retest system.
- Turn ignition off. Check continuity between TP sensor harness connector Black wire and engine ground. Also check circuit for short to voltage. Repair as necessary and retest system. See WIRING DIAGRAMS article. If ground circuit is okay, go to next step.
- Disconnect ECM harness connector. See Figure. Check continuity of Blue/White wire between TP sensor harness connector and ECM harness connector terminal No. 91. See Figure. Also check circuit for short to ground and short to voltage. Repair as necessary and retest system. If circuit is okay, go to next step.
- Reconnect harness connectors. Start engine and warm to normal operating temperature. Turn ignition off. Disconnect vacuum hose from throttle opener. See Fig 1. Using a hand vacuum pump, apply at least 11.81 in. Hg of vacuum to throttle opener. Ensure throttle drum is not contacting throttle opener rod. Turn ignition on. Measure voltage between ground and ECM terminal No. 91 by backprobing, with throttle in specified positions. See THROTTLE POSITION (TP) SENSOR VOLTAGE table. If voltage is as specified, go to step 7. If voltage is not as specified, go to next step.
- Adjust closed throttle position switch. See ON-VEHICLE ADJUSTMENTS article. Repeat step 5. If TP sensor voltage is still not as specified, replace TP sensor and retest system. If TP sensor voltage is okay, go to next step.
- Reconnect all harness connectors. Start engine and warm to normal operating temperature. Measure voltage between ground and ECM terminal No. 61 (White wire) by backprobing, with engine at specified speeds. See MASS AIRFLOW SENSOR VOLTAGE table under DTC P0100: MASS AIRFLOW (MAF) SENSOR. If voltage is as specified, go to next step. If voltage is not as specified, disconnect and reconnect MAF sensor harness connector and repeat test. If voltage is still not as specified, replace MAF sensor and retest system.
- Select DATA MONITOR with scan tool. Start engine and let it idle for at least 70 seconds. If DTC P0335 or P1336 is set, replace Crankshaft Position (CKP) sensor (POS) and retest system. If DTC P1335 is set, replace CKP sensor (REF) and retest system. If DTC P0335, P1335 or P1336 are not set, go to next step.
- Turn ignition off. Disconnect all injector harness connectors. 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) on any injector, replace appropriate injector and retest system.
- Turn ignition off. Disconnect connector F-46 (Blue, 12-pin J/C No. 18). See Figure. Check continuity between ground and connector F-46 terminal No. 2. See WIRING DIAGRAMS article. Also check circuit for short to voltage. Repair as necessary and retest system. If shield circuit is okay, go to next step.
- No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.
THROTTLE POSITION (TP) SENSOR VOLTAGE
| Throttle Position | Volts |
|---|---|
| Fully Closed | .15-.85 |
| Partially Opened | .15-.85 To 3.5-4.7 |
| Fully Opened | 3.5-4.7 |