Fuel & air metering · Powertrain · generic (SAE-defined)
P2122: Throttle/Pedal Position Sensor/Switch "D" Circuit Low
P2122 means the engine computer detected an abnormally low voltage signal from accelerator pedal position sensor D, usually the first sensor in the pedal assembly.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P2122 sets
Electronic throttle systems use two or more accelerator pedal position (APP) sensors so the powertrain control module (PCM) can cross-check driver input. If sensor D's signal voltage drops below its valid range, the PCM treats it as a circuit low fault and relies on the remaining sensor with reduced power. Voltage limits are manufacturer-specific.
Common causes of P2122
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Failed accelerator pedal position sensor
- Open or shorted-to-ground signal wire
- Loss of the sensor's reference voltage
- Corroded or loose pedal connector
- Chafed wiring near the pedal or firewall
- PCM fault (rare)
P2122 symptoms
- Check engine light and/or reduced power warning on
- Limp mode or limited acceleration
- Unresponsive or delayed accelerator
- Idle-only operation in some cases
How P2122 is diagnosed
- Scan for codes and freeze frame; look for other APP or reference voltage codes.
- Inspect the pedal connector and harness for damage, corrosion, or pinched wires.
- Watch both pedal sensor signals in live data while slowly pressing the pedal; look for dropouts.
- Check reference voltage and ground at the sensor connector.
- Test signal wire continuity and check for shorts to ground.
- Replace the pedal assembly only after wiring checks pass.
Typical fixes for P2122
- Replace the accelerator pedal assembly
- Repair the signal, reference, or ground wiring
- Clean or replace the pedal connector
- Address a shared reference voltage short from another sensor
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P2122 FAQ
What does code P2122 mean?
P2122 means the engine computer detected an abnormally low voltage signal from accelerator pedal position sensor D, usually the first sensor in the pedal assembly. The standard definition is "Throttle/Pedal Position Sensor/Switch "D" Circuit Low."
Can I drive with a P2122 code?
Drive only to a repair facility if the vehicle allows it. With a pedal sensor fault, many vehicles limit power or keep the engine near idle, which can be unsafe in traffic.
Is sensor D on the pedal or the throttle body?
In the SAE naming, sensors D, E, and F usually refer to accelerator pedal sensors, while A and B are typically at the throttle body; confirm with factory information.
Can another sensor cause P2122?
Yes. If a different sensor shorts the shared 5-volt reference, it can pull down the pedal sensor signal and set this code.
Keep researching
Engine guides by brand (known issues, specs)
More fuel & air metering codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.