P0120 code meaning
Throttle/Pedal Position Sensor/Switch A Circuit
Powertrain system Generic code P01xx codes Check engine light
What P0120 means
Sensor A is, in practice, throttle position sensor 1 at the throttle body; the accelerator pedal has its own codes (P2120 onwards). 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. P0120 is the general circuit fault, used when the fault cannot be classed as low or high or when the sensor is digital. Ford sets it on digital SENT throttle sensors when the sensor reports an error for more than 4 s, together with the MIL and wrench lamp; Saab Trionic used it as a collective code. GM and Ford's analogue throttles report P0122/P0123 instead. Electronic throttles then fall back to a spring-loaded limp position with limited power.
P0120 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0120
- Check engine light, on electronic throttles also wrench lamp
- Limp mode with reduced power ('Reduced Engine Power') on electronic throttles
- Raised or unsteady idle (cable systems)
- Poor throttle response, jerky driving
Common causes of P0120
- Most likelyConnector at the throttle body corroded or loose, broken wire
- PossibleSensor or throttle body with integrated sensor faulty
- Possible5 V reference disturbed (short on another sensor of the same circuit)
- Less likelyEngine control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Throttle position sensorThrottle bodySensor wiringSensor reference voltage
What each part of P0120 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 20 | The exact fault in that area. |
What to do next
- Note P0120 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0120
What does P0120 mean?
P0120 means "Throttle/Pedal Position Sensor/Switch A Circuit". Sensor A is, in practice, throttle position sensor 1 at the throttle body; the accelerator pedal has its own codes (P2120 onwards). It is a generic code, so it means the same on every make.
Is it safe to drive with P0120?
Drive gently and only to a workshop. With P0120 the car can go into limp mode (reduced power) to protect itself.
Will P0120 fail an emissions test?
Yes, it can. P0120 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0120 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0120 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.