Fuel & air metering · Powertrain · generic (SAE-defined)
P0122: Throttle/Pedal Position Sensor/Switch "A" Circuit Low
P0122 means the "A" throttle or pedal position sensor signal voltage is lower than the engine computer considers possible, usually due to a wiring or sensor fault.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0122 sets
The throttle position sensor (TPS) or pedal position sensor produces a low voltage at closed throttle that rises as it opens. The powertrain control module (PCM) sets P0122 if the "A" signal drops below the lowest plausible value for a set time. An open signal wire, a lost reference voltage, a short to ground or an internal sensor failure usually causes this. Voltage limits are manufacturer-specific.
Common causes of P0122
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Open or grounded signal wire
- Loss of reference voltage to the sensor
- Failed throttle position or pedal position sensor
- Corroded or loose connector
- Shorted sensor on a shared reference circuit
- Faulty throttle body assembly
P0122 symptoms
- Check engine light on
- Reduced power or limp mode
- Poor or no throttle response
- Stalling or rough idle
- Electronic throttle control warning light on some vehicles
How P0122 is diagnosed
- Scan for codes, especially reference voltage codes
- Inspect connectors and wiring at the throttle body or pedal
- Measure reference voltage and ground at the sensor
- Check the signal wire for opens or shorts to ground
- Watch the signal in live data while wiggling the harness
- Replace the sensor or throttle body if the circuit tests good
Typical fixes for P0122
- Repair open or grounded wiring
- Restore reference voltage by fixing a shorted shared sensor
- Replace the throttle position sensor
- Replace the electronic throttle body
- Perform a throttle relearn after repair
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.
Manufacturer notes
Older definitions read "Throttle/Pedal Position Sensor/Switch A Circuit Low Input". Definitions can vary by manufacturer; check factory service information.
Related codes & warning lights
P0122 FAQ
What does code P0122 mean?
P0122 means the "A" throttle or pedal position sensor signal voltage is lower than the engine computer considers possible, usually due to a wiring or sensor fault. The standard definition is "Throttle/Pedal Position Sensor/Switch "A" Circuit Low."
Can I drive with a P0122 code?
Only drive as much as necessary to reach a repair facility. The engine computer often limits power with this code, and acceleration may be poor or unpredictable.
What is the difference between P0122 and P0123?
P0122 means the sensor signal reads too low, often from an open or grounded wire, while P0123 means it reads too high, often from a short to voltage or an open ground.
Can unplugging the battery clear P0122?
It may clear the code temporarily, but the fault will return if the wiring or sensor problem remains.
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.