Faulty throttle position sensor or throttle body (worn track or internal electronics failure); Faulty accelerator pedal position sensor, where the pedal is the 'A' sensor on that model; Open circuit or high resistance in the signal or 5 V reference wire, or a poor connector terminal; Signal wire chafed and shorted to ground, or corroded or water-damaged connector; Loss of sensor reference supply or a poor sensor ground caused by a wiring fault; Fault inside the engine control unit.

P0122

Throttle/Pedal Position Sensor/Switch A Circuit Low.

Generic
Powertrain
Generic code
High severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
1: AreaFuel and air metering
22: FaultThe specific fault in that area

What it means

P0122 means the engine control unit has seen the signal voltage from throttle or pedal position sensor 'A' fall below the expected range, which points to a low-voltage fault in that circuit. The ECU compares the sensor signal against its plausible limits, and a reading near zero volts suggests an open circuit, a short to ground or a failed sensor. Which sensor is 'A' and how the car responds depends on the model and engine.

Symptoms

Engine warning light on
Car goes into limp mode with reduced power
Poor or no throttle response
Unstable, high or very low idle
Engine stalling or hesitating when pulling away
Cruise control not working

Possible causes

Faulty throttle position sensor or throttle body (worn track or internal electronics failure)likely
Faulty accelerator pedal position sensor, where the pedal is the 'A' sensor on that modellikely
Open circuit or high resistance in the signal or 5 V reference wire, or a poor connector terminallikely
Signal wire chafed and shorted to ground, or corroded or water-damaged connectorpossible
Loss of sensor reference supply or a poor sensor ground caused by a wiring faultpossible
Fault inside the engine control unitrare

How to diagnose

Read all stored and pending codes and freeze frame data, and note any other throttle, pedal or reference voltage codes.
Visually inspect the throttle body and pedal wiring and connectors for damage, chafing, corrosion, water ingress or loose terminals.
With live data, watch the throttle or pedal position reading and voltage from closed to fully open, looking for a flat low reading, dropouts or glitches.
Check that the throttle and pedal sensors agree with each other where the car shows both, as the model dictates.
With the sensor unplugged, check the reference supply and ground at the connector against the manufacturer's specification.
Test the signal wire for continuity to the ECU and for shorts to ground, with the battery disconnected and following the wiring diagram.
Wiggle the harness while watching live data to find intermittent faults.
Check the throttle body for heavy carbon build-up or sticking, which can affect the reading on some designs.

How to fix

Repair or replace damaged wiring, and clean or replace corroded or loose connector terminals.
Replace the faulty throttle body or throttle position sensor, as the design allows.
Replace the faulty accelerator pedal assembly if the pedal sensor is at fault.
Restore a missing reference supply or ground by repairing the harness fault.
After repair, clear the codes and carry out the throttle adaptation or relearn procedure the manufacturer specifies for the model.
Have the ECU checked only after all wiring and sensor faults have been ruled out.

Can I keep driving?

High severity

Avoid driving if you can, because the car may lose power unexpectedly or stall, which is unsafe in traffic. If it must be moved, drive only a short distance to a safe place or a workshop.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.