P2138: Throttle or pedal position sensors D and E voltage mismatch

What P2138 means

For safety, the position on the accelerator pedal is measured by two sensors at once, and the ECU checks that their signals say the same thing. This code means sensors D and E disagree, so the ECU cannot tell which to believe and cuts power. On most cars sensors D and E are the pedal ones.

Most common causes

• Dirty, loose or corroded accelerator pedal connector
• A poor contact on one sensor wire or a faulty shared ground
• A worn pedal sensor (usually the whole pedal unit is replaced)
• A floor mat rubbing on the pedal
• A fault in the engine ECU, which is uncommon

Symptoms

• Engine or throttle warning light on
• Reduced power or limp mode
• Odd or jerky throttle response
• High or unstable idle

Can you drive with P2138?

With care You can usually drive with care and reduced power. See a garage soon, as the car may drop to idle without warning.

How to check it

Use a live data reader to watch both pedal signals while slowly pressing the pedal to the floor: they should move together. If one drifts away or jumps at some point, the pedal or its connector is the suspect.

How to read and clear P2138 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P2138 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

• P2125 Throttle or pedal position sensor E circuit fault
• P2127 Throttle or pedal position sensor E circuit low
• P2128 Throttle or pedal position sensor E circuit high
• P2135 Throttle or pedal position sensors A and B voltage mismatch
• P2146 Fuel injector group A supply voltage circuit or open
• P2177 System too lean off idle (bank 1)
• P2178 Mixture too rich away from idle (bank 1)
• P2179 Mixture too lean away from idle (bank 2)
• P2100 Throttle actuator A control motor circuit open
• P2101 Throttle actuator A control motor circuit range or performance
• P2102 Throttle actuator A control motor circuit low
• P2104 Throttle control system: forced idle

P2138 is a generic code, so it means the same on any make, for example on Audi, Fiat, Mazda, Peugeot, Toyota, Volkswagen. See what Final OBD does on your car in makes and models.