P2128 fault code: what it means

P2128: Accelerator pedal sensor 2 (G185) signal too high. Reduced power; a shorted oxygen sensor can also cause it.

Engine and gearbox (powertrain) · Costly if missed

Usual causes, most likely first

wiring fault
faulty oxygen sensor on the shared 5 V supply
faulty accelerator pedal
engine computer fault

P2128 by make

Audi

Accelerator pedal sensor 2 (G185) signal too high. Reduced power; a shorted oxygen sensor can also cause it.

Usual causes: wiring fault; faulty oxygen sensor on the shared 5 V supply; faulty accelerator pedal; engine computer fault

Honda

Accelerator pedal position sensor B circuit high. Limp mode possible.

Usual causes: accelerator pedal sensor; wiring fault

Isuzu

Accelerator pedal sensor 2 circuit high.

Usual causes: pedal sensor; wiring

Mazda

Accelerator pedal position sensor No.2 circuit high. Limp mode with limited power.

Usual causes: accelerator pedal assembly; wiring or connector fault

Skoda

Accelerator pedal sensor 2 (G185) signal too high. Reduced power; a shorted oxygen sensor can also cause it.

Usual causes: wiring fault; faulty oxygen sensor on the shared 5 V supply; faulty accelerator pedal; engine computer fault

Subaru

Accelerator pedal sensor E circuit high.

Usual causes: accelerator pedal assembly; wiring fault

Volkswagen

Accelerator pedal sensor 2 (G185) signal too high. Reduced power; a shorted oxygen sensor can also cause it.

Usual causes: wiring fault; faulty oxygen sensor on the shared 5 V supply; faulty accelerator pedal; engine computer fault

What the repair usually costs

Air-fuel ratio / front O2 sensor replace (upstream)NZ$270–NZ$750 · A$260–A$730
O2 sensor replace (downstream / after cat)NZ$180–NZ$480 · A$180–A$460

Not sure what P2128 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.