Fuel and air

P0122 — Throttle Position Sensor A Circuit Low Input

Severity: medium Drive with care, to a shop

What P0122 means

The engine control module reads the voltage from throttle (or pedal) position sensor A to know how far the throttle is open. P0122 sets when that signal stays below the expected range. Typical causes are an open or grounded signal wire, lost sensor reference voltage, or a failed sensor.

Symptoms

  • Check Engine light on
  • Sluggish or delayed acceleration
  • Rough, high or low idle
  • Stalling or hesitation when pressing the pedal
  • Poor throttle response
  • Limp mode with reduced power

Possible causes

  1. Failed throttle or pedal position sensor
  2. Damaged, chafed or corroded wiring and connector terminals
  3. Signal wire shorted to ground
  4. Open in the 5 V reference supply to the sensor
  5. Loose connector at the throttle body
  6. Sensor installed incorrectly or misaligned
  7. ECM fault (rare)

How to diagnose

  1. Scan for codes and freeze-frame data, and note any other throttle or sensor codes.
  2. Inspect the throttle body connector and harness for chafing, corrosion, moisture and a loose fit.
  3. With a scan tool, watch the sensor voltage at closed throttle and while slowly pressing the pedal; it should change smoothly with no dropouts to zero.
  4. Unplug the connector and use a multimeter to check for 5 V reference and a good ground.
  5. Test the signal wire to the ECM for opens and for shorts to ground.
  6. Check that the throttle body is clean and moves freely, and that the sensor is seated correctly.
  7. If wiring tests good, test or replace the sensor, and suspect the ECM only as a last step.

Common fixes

  • Replace the throttle or pedal position sensor
  • Repair the wiring or replace the damaged connector or terminals
  • Reinstall the sensor correctly and run a throttle relearn with a scan tool if needed
  • Replace or reflash the ECM if confirmed faulty

Questions and answers

What does P0122 mean?

The ECM is getting too low a voltage from throttle position sensor A. The usual causes are a bad sensor or an open or grounded wire.

Can I drive with P0122?

Only a short distance, for example to a repair shop. The engine may stall or lose power without warning, which is dangerous in traffic.

How do I fix P0122?

Start by inspecting the sensor connector and wiring, then test reference voltage and signal with a multimeter. If the wiring is fine, replace the sensor, clear the code and perform a throttle relearn if required.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.