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.