Is P2138 the accelerator pedal or the throttle body?

On almost every car it is the accelerator pedal circuit: the pedal sensors are labelled D and E, while the throttle body sensors are A and B and set P2135 when they disagree. The pedal sensors are usually built into the pedal assembly, so the common fix is a new pedal unless the connector or wiring is at fault.

Can I drive with P2138?

Only gently and only as far as you need to. Many cars hold a raised idle or respond very weakly to the pedal, so you cannot count on power when pulling out or overtaking. Get the car to a workshop or a safe place and have it fixed before using it normally.

Can a weak battery cause P2138?

It can contribute. If the system voltage dips, for example on a failing battery or with a poor ground, the supply to the pedal sensors can become unstable and the two signals can briefly disagree. Test the battery and grounds before replacing the pedal, especially if other sensor codes appeared at the same time.

How much does it cost to fix P2138?

A new accelerator pedal assembly costs 130 to 380 euros fitted, and it is a straightforward job on most cars. Cleaning and reseating the connector costs nothing to 50 euros, and a wiring repair runs 70 to 220 euros, mostly fault-finding time.

P2138: Throttle/Pedal Position Sensor/Switch "D"/"E" Voltage Correlation

Quick Answer

Not safe to drive

P2138 means the two sensors inside the accelerator pedal, sensor "D" and sensor "E", are sending voltages that no longer agree. On a drive-by-wire car the pedal has no cable to the engine: these two sensors tell the engine computer how far you are pressing, and it compares them constantly as a safety check. When they disagree it cannot trust your pedal input, so it limits power, often to little more than a raised idle. The usual causes are a worn pedal sensor, a connector or wiring fault at the pedal, or an unstable supply voltage.

Severity: High · Electrical

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What does P2138 mean?

P2138 is a electrical-related diagnostic trouble code classified as high severity. When your vehicle's ECU detects this condition, it stores P2138 and illuminates the check engine light.

What are the symptoms of P2138?

If your vehicle has triggered P2138, you may notice one or more of these symptoms:

EPC light (on Volkswagen group cars) or check engine light on, often with a reduced power message
Car barely accelerates, or holds a raised idle whatever you do with the pedal
Delayed or uneven response when you press the accelerator
Cruise control switched off
Fault that comes and goes, sometimes only at a certain pedal position

What causes P2138?

Here are the most common causes of P2138:

Worn sensor track inside the accelerator pedal assembly
: high
Corroded, loose or damaged connector at the pedal, sometimes from water in the footwell
: high
Chafed or broken wire between the pedal and the engine computer
: medium
Weak 5 V reference or ground to the pedal sensors
: medium
Low battery voltage or a poor ground upsetting the sensor signals
: low
Engine computer fault (rare)
: low

Is it safe to drive with P2138?

No - address this immediately. Not safe for normal driving. With the two pedal signals in disagreement, the engine computer may ignore the pedal almost entirely or respond very slowly, so you cannot rely on the car to accelerate when you need it to. Drive only gently to a safe place or a nearby workshop, and avoid motorways, overtaking and junctions where you need to pull away quickly.

How do you diagnose P2138?

Follow these steps to pinpoint the root cause of P2138:

Read all stored codes and the freeze frame. Codes for the individual pedal sensor circuits, or other low-input codes that suggest a shared 5 V reference problem, often appear alongside and narrow down the fault. A generic OBD2 reader shows the codes, the freeze frame and, where the engine computer reports them, the standard accelerator pedal position readings D and E.
With the ignition on and the engine off, watch both pedal readings while pressing the pedal slowly from rest to the floor. They should both change smoothly and in step, often on different scales; a jump, flat spot or dropout in either one points to the pedal sensor or its wiring.
Unplug the connector at the pedal and check for corrosion, water and pushed-back pins. Check the footwell carpet for damp, which can come from a blocked drain or a leaking seal.
Back-probe the connector with the ignition on: on most cars each pedal sensor has its own 5 V reference and ground, and both should be present. A missing reference points to the wiring or to another fault dragging the supply down.
Wiggle the harness from the pedal towards the engine computer while watching the readings to catch an intermittent break.
If the supply and wiring are good, replace the accelerator pedal assembly; on most modern cars the sensors are built into it. Some makes then need a pedal or throttle adaptation, which may require manufacturer-level software rather than a generic OBD2 reader. Clear the code and road-test with slow and quick pedal presses.

How much does P2138 cost to fix?

Repair costs for P2138 vary depending on the root cause and your vehicle. Here are typical estimates:

Repair	Parts Cost	Labor Cost	Total Estimate	DIY Difficulty
Replace accelerator pedal assembly (drive-by-wire)	€90–€280	€40–€100	€130–€380	Easy
Clean and reseat pedal connector	€0–€10	€0–€40	€0–€50	Easy
Repair pedal sensor wiring or connector	€10–€40	€60–€180	€70–€220	Moderate

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

These codes are often seen alongside P2138 or indicate related issues:

Common questions about P2138

What does P2138 mean?: P2138 means the two sensors inside the accelerator pedal, sensor "D" and sensor "E", are reporting pedal positions that do not agree. The engine computer compares them as a safety check, and when they disagree it no longer trusts your pedal input, so it limits power.
Is P2138 the accelerator pedal or the throttle body?: On almost every car it is the accelerator pedal circuit: the pedal sensors are labelled D and E, while the throttle body sensors are A and B and set P2135 when they disagree. The pedal sensors are usually built into the pedal assembly, so the common fix is a new pedal unless the connector or wiring is at fault.
Can I drive with P2138?: Only gently and only as far as you need to. Many cars hold a raised idle or respond very weakly to the pedal, so you cannot count on power when pulling out or overtaking. Get the car to a workshop or a safe place and have it fixed before using it normally.
Can a weak battery cause P2138?: It can contribute. If the system voltage dips, for example on a failing battery or with a poor ground, the supply to the pedal sensors can become unstable and the two signals can briefly disagree. Test the battery and grounds before replacing the pedal, especially if other sensor codes appeared at the same time.
How much does it cost to fix P2138?: A new accelerator pedal assembly costs 130 to 380 euros fitted, and it is a straightforward job on most cars. Cleaning and reseating the connector costs nothing to 50 euros, and a wiring repair runs 70 to 220 euros, mostly fault-finding time.

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