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Throttle/Pedal Position Sensor 'A' Low Input

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What P0122 means

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The control unit reports “Throttle/Pedal Position Sensor 'A' Low Input”. Code P0122 identifies the area to investigate, but it does not prove that one named part has failed without a confirming test and vehicle context.

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General information, not a diagnosis or repair instruction. Always confirm with a qualified mechanic for your specific vehicle.

For a code naming the throttle position system, read it alongside the conditions it appeared under before deciding anything.

What this code does not prove

A code naming the throttle position system reports what the control unit observed, not which part caused it. More than one cause can trigger the same code, so testing has to separate them.

Where the diagnosis usually goes next

Check the signal at its source

The throttle position system is what code P0122 is reporting on — specifically, the signal reads at or near the bottom of its expected electrical range. This points to an area, not a confirmed cause.

How to tell the paths apart: Read the live data and compare it against the expected range for current conditions before replacing anything.

Rule out wiring and the connector

Codes of this shape often come from damaged wiring, a corroded connector, or a poor ground on the throttle position system — not the component itself.

How to tell the paths apart: Inspect the wiring and connector for the throttle position system for damage and a secure ground before replacing anything.

Before you drive on

By itself, a code naming the throttle position system does not settle whether this specific car is safe to keep driving. Normal behaviour means limited use for diagnosis only; any change resets that decision.

Stop and arrange a check if

  • the engine is misfiring, losing power, or stalling
  • smoke, a fuel/burning smell, or overheating appears
  • the throttle position system's behaviour is clearly getting worse rather than staying stable

Before authorising a repair

  • Bring the complete code list and freeze-frame data relevant to the throttle position system
  • Ask for the test that confirms a fault in the throttle position system — not just the code alone

What to check first

  1. Pull up live data on the throttle position system and see how it compares with the range expected for the current conditions.
  2. Inspect the wiring, connector, and ground for the throttle position system before replacing the component.
  3. A throttle/pedal position signal should move smoothly and proportionally from idle to wide-open throttle with no gaps, flat spots, or sudden jumps, and two redundant sensor tracks (where fitted) should stay in a fixed relationship to each other through the full range. A signal that skips, plateaus mid-travel, or where the two tracks drift apart points to the sensor, its linkage, or its wiring rather than the engine's response — sweeping the pedal slowly while watching live data is the standard way to catch this.
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Frequently asked questions

Does this code tell me the throttle position system has failed?

No. It points to the throttle position system; the cause still needs to be confirmed by a measurement or targeted test.

What should I bring to the workshop?

The complete code list, freeze-frame data, and the conditions around the throttle position system — that gives the technician context, not a guess.

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