DTC P1120: Throttle Position (TP) Sensor: Condition

DTC P1120 indicates TP sensor closed throttle position is less than range of 3.4 percent (.17 volt) Possible causes for this fault are:

• Damaged wiring harness or connectors.
• Open in VREF circuit.
• Faulty TP sensor.
• Faulty Powertrain Control Module (PCM).

1. Check For Binding Throttle Plate
   
   Inspect TP sensor connector for damage or corrosion. Inspect wiring harness between TP sensor and PCM for damage or corrosion. Repair as necessary, and repeat QUICK TEST. See TESTS W/CODES - INTRODUCTION article. If no mechanical problem is found, go to next step.
2. Check For Stuck TP Sensor
   
   Turn ignition off. Connect scan tool to DLC. Access TP PID on scan tool. While observing TP PID, slowly move throttle through range from closed to wide open throttle. If TP PID indicates any sudden drops to below 0.49 volt, go to next step. If TP PID increase and decrease is gradual and smooth, go to step 1) in DTC P1125.
3. Check VREF Circuit Voltage
   
   With TP sensor disconnected, turn ignition on. Measure voltage between VREF and SIG RTN terminals at TP sensor wiring harness connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, check for open or short in VREF circuit. Repair as needed.
4. Check TP Circuit Resistance
   
   Turn ignition off. Leave TP sensor disconnected. Disconnect PCM 104-pin connector. Inspect connector for damage and repair as necessary. Install Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 89 (TP) and TP terminal of TP sensor wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in TP circuit.
5. Check TP Sensor Signal To PCM
   
   Turn ignition off. Connect PCM to breakout box. Start engine and idle for 2 minutes. While slowly opening throttle, measure voltage between test pins No. 89 (TP) and 91 (SIG RTN) at breakout box. If at any time voltage enters 0.17-0.49 volt range, replace TP sensor. If voltage does not enter 0.17-0.49 volt range, go to next step.