EngineLightCodes
Powertrain code

P0122 Throttle/Pedal Position Sensor/Switch A Circuit Low

Severity
Fix soon
Typical repair cost
$20–$500
Do it yourself
Possible, medium
Shop time
0.5–2 hours

Sensor A is, in practice, throttle position sensor 1 at the throttle body; the accelerator pedal has its own codes (P2120 onwards).

How the engine computer detects it

With a cable-operated throttle there is a single potentiometer (about 0.5 V closed to 4.5 V wide open). Electronic throttles have two sensors sharing a 5 V reference and ground, usually running in opposite directions – on GM throttle sensor 1 falls from 3–4 V at idle to below 1 V at full throttle. P0122 means the signal voltage of sensor A is below its lower limit – electrically meant, not 'throttle closed': typically an open or grounded signal wire or a missing 5 V reference. Limits: Ford below 0.25 V (detected within 1 s), Saab/GM 2011 below 0.3 V for 1 s, Saab cable system below 0.2 V for 5 s. GM treats it as a one-trip fault and switches to reduced engine power; Ford lights the MIL and wrench lamp and continues on the remaining sensor or in limp mode.

Written from public technical sources and not yet checked by a mechanic. How we write these pages

Symptoms

  • Check engine light, on electronic throttles also wrench lamp
  • Limp mode with reduced power ('Reduced Engine Power') on electronic throttles
  • Engine barely responds to the pedal or stalls at idle
  • High idle, A/C switched off (cable systems)

Common causes

  1. Signal wire open or shorted to ground Most likely
  2. Connector at the throttle body loose or corroded Most likely
  3. 5 V reference missing (open, or shorted by another sensor) Possible
  4. Sensor or throttle body faulty Possible
  5. Engine control module faulty Less likely

How to diagnose P0122

  1. Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
  2. Inspect the parts involved: throttle position sensor, throttle body, sensor wiring, sensor reference voltage.
  3. Work through the causes above from most to least likely, cheapest checks first.
  4. Clear the code and drive a full drive cycle to confirm the repair held.

Reading the code

P
Powertrain
0
Generic (SAE) code
1
Fuel and air metering
22
Specific fault

Questions drivers ask

Can I drive with code P0122?

Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.

Will my car pass an emissions inspection with P0122?

Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.

Can I fix P0122 myself?

Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.

Often reported together

Codes that owners mention in the same NHTSA complaints as P0122. They can point to a shared cause, so it's worth checking them together.

This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.