P2135: Throttle/pedal position sensor "A"/"B" voltage correlation
On cars with an electronic throttle, the throttle and the accelerator pedal each have two or more position sensors that should agree. Two of them don’t, so the engine computer can’t trust the reading and often limits the power (limp mode).
Updated
What P2135 means
On cars with an electronic throttle, the throttle and the accelerator pedal each have at least two position sensors, so the engine computer can check one against the other. When you press the pedal, their signals should change together.
P2135 means the signals of sensors “A” and “B” don’t agree. On many cars these are the two sensors in the throttle body, but it depends on the car. Because it can’t tell which one is right, the engine computer usually limits the power (limp mode) to be on the safe side.
P2136 to P2139: other pairs of sensors
P2136 (A/C), P2137 (B/C), P2138 (D/E) and P2139 (D/F) are the same check for other pairs. On many cars “D” and “E” are the two sensors in the accelerator pedal, so P2138 there points to the pedal or its wiring. The service information for your car says which sensor is which.
P2136: Throttle/Pedal Position Sensor A/C Voltage Correlation
P2137: Throttle/Pedal Position Sensor B/C Voltage Correlation
P2138: Throttle/pedal position sensor "D"/"E" voltage correlation
P2139: Throttle/Pedal Position Sensor/Switch D/F Voltage Correlation
Can I keep driving?
Drive gently
Drive gently and only as far as you need to, and have it checked soon. The engine computer may cut the power (limp mode) or let the engine only idle, sometimes suddenly, so avoid motorways and overtaking until it’s fixed. If the engine stalls, or doesn’t respond to the pedal as it should, stop when it’s safe to do so and have it recovered.
General guidance based on the code alone, not on the car’s actual condition. If in doubt, stop and ask a mechanic.
The power can drop suddenly, for example while overtaking or joining a motorway, so avoid those until it’s fixed.
Symptoms
- Limp mode: less power, or the engine won’t rev above a limit.
- Poor or no response to the accelerator pedal.
- Stalling or an uneven idle on some cars.
- Cruise control not working on some cars.
Common causes
- Faulty throttle body or throttle position sensor. The sensors are usually built into the throttle body, which is then replaced as a unit.
- Faulty accelerator pedal sensor. Wear in the pedal sensor can make one signal jump. The sensor is usually part of the pedal assembly.
- Wiring or connector fault, such as corrosion. A common cause. Water getting into a connector, for example past a leaking seal, can corrode the pins.
- Poor earth connection. A poor earth distorts the sensors’ signals.
Typical fixes
- Read all fault codes, and find out from the service information whether the sensors named are in the throttle or the pedal on your car.
- Check the connectors at the throttle body and the pedal for corrosion, water and a firm fit, and the wiring for chafing.
- Have both signals compared with a diagnostic tool while the pedal is pressed slowly: a jump or gap points to the faulty part.
- Replace the faulty throttle body or pedal. Some cars then need a relearn, with a tool for the make.
Questions
Can I drive with P2135?
Gently, and only as far as you need to. The engine computer may cut the power or let the engine only idle, sometimes suddenly, so avoid motorways and overtaking. If the engine stalls or doesn’t respond to the pedal as it should, stop when it’s safe to do so and have it recovered.
What is the difference between P2135 and P0120?
P0120 means one sensor’s signal is missing or out of range. P2135 means two signals that are each within range don’t agree with each other. The causes overlap.