P0122: Throttle - Pedal Position Sensor - Switch A Circuit Low Input

What is the engine computer reporting with P0122?

The computer reads a voltage from the throttle position sensor circuit lower than any plausible throttle angle, which usually means an open circuit, a disconnected sensor, or a short to ground.

The code sits in the throttle position sensor circuit area and is reported by the comprehensive component monitor. It names the circuit or the condition where the computer saw a reading outside its expected range. It does not name a failed part, and several genuinely different faults set this same code, which is the whole reason the causes below are ordered rather than listed.

What people usually notice

• Reduced power or limp mode
• Rough or unstable idle
• Hesitation on acceleration
• Check engine light

What is actually behind P0122?

The causes below are ordered by how often they turn out to be the answer, cheapest and most common first. That order matters more than the list itself: the expensive component named in the code text is very rarely the first thing to replace, and working down from the top is what stops a throttle position sensor circuit fault becoming an expensive guess.

Disconnected or corroded connector at the sensor is the one to rule out before anything else. The simplest and most common cause to check first.

How do you diagnose P0122?

Start with freeze frame. Throttle position value at the fault shows how far below a plausible reading the signal fell. That snapshot is taken at the instant the code set, and it is the single most useful piece of evidence you have, which is also why clearing the code before reading it is such a costly habit.

This code is diagnosed by watching values change rather than by reading the number again, so the tool has to stream live data and hold freeze frame. Reading live sensor voltage while operating the throttle confirms whether the signal is truly stuck low or intermittently dropping out.

The order worth working in

• 1. Disconnected or corroded connector at the sensor: The simplest and most common cause to check first.
• 2. Broken or shorted wire in the sensor signal circuit: Chafing near the throttle body is a frequent culprit.
• 3. Failed sensor with no usable output: A dead sensor element reads as a low or absent signal.
• 4. Corroded connector pins: Common in engine bays exposed to moisture.

Can you keep driving with P0122?

Expect a reduced power limp mode on many vehicles, so limit driving until this is checked.

This is a severity 3 of 4 code, which means continuing to drive normally risks damage that costs considerably more than the repair in front of you. Treat the lamp as an instruction rather than a notification.

What does it cost to ignore P0122?

This code frequently forces a safety limp mode, and continued driving in that state means accepting unpredictable, reduced power until repaired.

There is also the diagnostic cost of waiting. Freeze frame data, pending code history and the readiness monitor state all describe the fault as it was when it set, and all of it is lost the moment somebody clears the code to make the lamp go out.