P0122 serious

Throttle/Pedal Position Sensor A Circuit Low Input

What does P0122 mean?

The P0122 code means the vehicle's onboard diagnostic system has detected: Throttle/Pedal Position Sensor A Circuit Low Input. This is a serious severity code.

Common Symptoms

  • Check Engine Light on
  • Reduced throttle response
  • Engine may idle high or low
  • Possible limp mode
  • Hesitation under acceleration

Probable Causes (Ranked by Likelihood)

  • TPS signal voltage below minimum threshold Very High
  • Short to ground in TPS signal wire High
  • Broken or shorted TPS internals High
  • Missing 5V reference voltage to TPS Moderate

Step-by-Step Diagnostic Procedure

  1. Check TPS signal voltage at rest. Below 0.2V indicates a low signal fault.

  2. Verify 5V reference supply at the TPS connector pin.

  3. Disconnect TPS. If voltage at signal wire goes to 5V, the TPS is shorting the signal low.

  4. Check wiring for shorts to ground.

  5. Replace TPS if reference is present but signal remains low.

Frequently Asked Questions

Will P0122 put my car in limp mode?

On many vehicles, yes. When the throttle position sensor reads below its minimum valid voltage, the ECU cannot determine throttle angle and may default to a fixed, limited throttle opening to allow the car to limp home.

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