P2109: Throttle/Pedal Position Sensor A Minimum Stop Performance

What it means

The ECU detects that the throttle position sensor A signal at the closed-throttle stop does not match the learned minimum value. The mechanical or electrical zero reference of the throttle has drifted out of the expected range, often after cleaning, replacement or wear.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

Throttle position sensor A reports the throttle plate's position, including its closed-throttle reference. P2109 sets when the control module finds sensor A's signal at the minimum stop outside the learned or expected range, which can follow buildup, sensor drift, or a missed relearn.

Common causes

Most likely first.

1. Carbon deposits on throttle plate
2. Throttle position sensor drift
3. Idle/throttle relearn not performed

Symptoms

• Check engine light on
• Reduced throttle response, possible limp mode
• Hesitation or surging
• Idle too high or too low

How to diagnose it

1. Save freeze-frame data and compare live throttle-position sensor A readings at the closed stop with the learned minimum and any related sensor codes.
2. Inspect the throttle plate and bore for deposits that may keep the plate from reaching its normal resting position.
3. Check the throttle-position sensor A connector and wiring for corrosion, loose terminals, or damage that could shift its signal.
4. If the throttle body was recently cleaned or replaced, check whether the manufacturer's throttle or idle relearn procedure is required and has been completed.
5. If cleaning, wiring, and relearn do not resolve the fault, test sensor A and the throttle body's minimum-stop operation against the manufacturer's specification.

Common fixes

• Clean deposits from the throttle plate and bore using the manufacturer's approved method.
• Repair a poor connection or damaged wire in the throttle-position sensor A circuit.
• Perform the required throttle or idle relearn after cleaning or throttle-body service.
• Replace the throttle-position sensor or throttle body if testing confirms sensor A has drifted or failed.

Can I keep driving?

Reduced power, unstable idle, or hesitation can make acceleration unpredictable; avoid high-speed driving until the throttle returns to normal. If the engine stalls or will not idle safely, stop and arrange assistance.