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P1120 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P1120 is an OBD-II Code that refers to Throttle Position Sensor Out Of Range (Ford, Lincoln, Mercury)

Meaning

A P1120 code is a manufacturer specific diagnostic trouble code that occurs with Ford, Lincoln, Mercury and related makes and vehicles when the ECM/PCM detects a problem with the range or position of the throttle position sensor (TPS). The throttle position sensor signal is used by the ECM/PCM to determine how much throttle opening is required for various engine operating conditions. 

When the P1120 code is set, it means that there is an issue with the TPS signal being either too low or too high when compared to what the ECM/PCM is expecting.

Causes

Common causes for this code include:

  • Electrical issue with the throttle position sensor circuit
  • Dirty or contaminated throttle body
  • Faulty throttle position sensor
  • Faulty throttle body motor

Symptoms

The symptoms of a P1120 code are:

Diagnosis

To diagnose a P1120 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect the electrical connectors and wiring for the throttle position sensor and throttle body.
  3. Check for voltage, ground and continuity in the throttle position sensor circuit.
  4. Test the operation of the throttle position sensor and compare it to reference values.
  5. Inspect the throttle body for dirt or debris that may be interfering with proper movement of the throttle plate.
  6. Compare all data with manufacturer’s reference values.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P1120 code:

  • Not thoroughly inspecting all the wiring and connectors for damage or loose connections
  • Not properly testing the throttle position sensor or comparing it to reference values
  • replacing the throttle position sensor without first checking for other possible causes
  • Failing to properly clean the throttle body before installing a new throttle position sensor

How serious is this?

A P1120 code is a serious code because it can cause the engine to run erratically or stall. This can be very dangerous, especially if it happens while driving.

What repairs can fix the code?

repair manuals

The following are solutions that may fix this problem:

  • Broken or faulty wirings must be repaired or replaced as needed
  • A new throttle position sensor may need to be installed
  • The throttle body may need to be cleaned or replaced
  • The ECM/PCM may need to be reprogrammed

Related codes

A P1120 is related to and may be accompanied by the following codes:

P1121 – Throttle Position Sensor Out of Range Low (Ford, Lincoln, Mercury)

P1122 – Throttle Position Sensor Out of Range High (Ford, Lincoln, Mercury)

P0122 – Throttle Position Sensor Circuit Low Voltage (Generic Powertrain)

Conclusion

In conclusion, the P1120 code is a diagnostic trouble code that refers to a problem with the throttle position sensor signal being either too low or too high. This can be caused by a number of different issues, such as electrical problems, dirty or contaminated throttle bodies, or faulty sensors. If you are experiencing any of the symptoms associated with this code, it is important to have your vehicle diagnosed and repaired as soon as possible to avoid any further damage.