Engine
What does the throttle body do and why does a fault trigger limp mode?
On modern cars the accelerator pedal does not move the throttle with a cable: it sends a signal to the control unit, which opens the throttle with an electric motor. If it detects that the throttle or pedal sensors disagree, it limits power or rpm for safety (limp mode) and stores codes such as P2135, P2106 or P2110.
Reviewed by Daniel Morales, founder of Reprorace SL, on
Why are there two sensors in each place?
For safety, the pedal and the throttle each have two position tracks. The control unit compares them all the time: if they do not match, it cannot know what the driver wants and cuts power.
What causes the faults?
Carbon in the throttle body, which slows it or changes the idle; worn sensors; loose or corroded connectors; and sometimes low battery voltage.
After cleaning or replacing the throttle body, many cars need a relearn with a diagnostic tool or a manufacturer procedure.
What should I do if the car goes into limp mode?
Find a safe place, stop and switch off; sometimes, after restarting, power returns until the fault comes back. Read the code and take it to a workshop.
On diesels, the intake throttle also shuts the engine down smoothly and helps the EGR, and it has its own codes.
General guidance only: every manufacturer and model has its own details. Always follow your vehicle's manual and, if in doubt, ask a workshop.
Related
Related trouble codes
- P2135Throttle/pedal position sensor/switch A/B voltage: correlation fault
- P0121Throttle/pedal position sensor/switch A, circuit: range/performance
- P2106Throttle actuator control system: forced power limitation
- P2110Throttle actuator A control system: forced engine speed limitation
- P2111Throttle actuator A control system: stuck open
- P0505Idle control system: malfunction
Related symptoms
- Car loses power: what limp mode is
- Rough idle: why the engine shakes or hunts when stationary
- Car stalls by itself: causes and what to do
Learn more
See what your car is saying
With the ECO-LITE you see the code as soon as it appears, and your workshop can check remotely, if the car publishes them, the pedal and throttle positions live.
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Frequently asked questions
Is an electronic pedal fault dangerous?
The control unit limits power to keep it safe, but drive carefully to the workshop.
Does cleaning the throttle body fix the idle?
Sometimes. Afterward a relearn may be needed so the control unit recognizes the new position.
What does P2135 mean?
That the two position signals of the throttle or the pedal do not agree as they should.