What does code P2123 mean?

P2123 means pedal sensor D's signal is stuck high: short to voltage or lost ground at the pedal. It’s serious: diagnose it promptly to avoid expensive damage.

What does P2123 mean in plain words?

Pedal sensor D's signal is stuck high: short to voltage or lost ground at the pedal. Wiring first: footwell harnesses suffer spills, kicks, and rodents; the sealed pedal assembly is the second suspect.

Can I just clear it and drive?

It returns: pedal plausibility is checked continuously. Clearing is for confirming a repair, not living with one missing.

Pedal assembly or throttle body: which am I buying?

P2122–P2128 = pedal-side sensors (the pedal assembly). P0120-family and P2135 = throttle-body-side. The code prefix decides which end of the wire you're shopping for.

P2123: Accelerator Pedal Position Sensor D Circuit High

Severe

Quick answer

P2123 means pedal sensor D's signal is stuck high: short to voltage or lost ground at the pedal. First move: wiring first: footwell harnesses suffer spills, kicks, and rodents; the sealed pedal assembly is the second suspect.

What it means

P2123 reports that pedal sensor D's signal is stuck high: short to voltage or lost ground at the pedal.

Drive-by-wire pedals carry two redundant position sensors precisely so a single lying sensor can never command acceleration. When either circuit misbehaves, the computer responds with reduced power, annoying by design, because the failure mode being prevented is unintended throttle.

The steps below run cheapest-first, because in this family, the cheap causes really are the common ones.

P2123 symptoms: what you'll notice

Sudden loss of throttle response: the computer drops into reduced power and ignores most of what your foot asks.
A reduced-power or wrench warning lights up on the dash along with the check engine light.
Acceleration capped at a crawl; merging or climbing hills becomes genuinely unsafe.
On some cars the problem comes and goes with bumps or footwell movement: a wiring clue.

Common causes

Ordered from most to least likely.

1.

See the diagnosis steps

This family shares its suspect list; the steps walk it in cost order.
2.

Wiring or connector damage

The universal suspect for circuit-flavored codes.
3.

The component named by the code

Condemned by measurement, never by guess.

How to fix it: diagnosis, step by step

Cheapest and most likely checks first.

1 Respect the limp mode

Reduced power with these codes is the system working. Drive gently or not at all until diagnosed: highway merges in limp mode are their own hazard.
2 Inspect the footwell

The pedal's connector and harness live where drinks spill, boots kick, and rodents visit. Unplug, inspect pins, reseat: a high percentage of pedal codes end here.
3 Watch both signals

On a scanner showing both pedal channels, sweep slowly: two smooth traces in their designed relationship = circuits fine (recheck connector); a dropout in one channel = that sensor, which means the sealed pedal assembly.

Parts & tools you may need

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Related codes

Frequently asked questions

What does code P2123 mean?: P2123 means pedal sensor D's signal is stuck high: short to voltage or lost ground at the pedal. It’s serious: diagnose it promptly to avoid expensive damage.
What does P2123 mean in plain words?: Pedal sensor D's signal is stuck high: short to voltage or lost ground at the pedal. Wiring first: footwell harnesses suffer spills, kicks, and rodents; the sealed pedal assembly is the second suspect.
Can I just clear it and drive?: It returns: pedal plausibility is checked continuously. Clearing is for confirming a repair, not living with one missing.
Pedal assembly or throttle body: which am I buying?: P2122–P2128 = pedal-side sensors (the pedal assembly). P0120-family and P2135 = throttle-body-side. The code prefix decides which end of the wire you're shopping for.