P2138: Throttle/Pedal Position Sensor/Switch "D"/"E" Voltage Correlation
The two sensors in the accelerator pedal that report how far you are pressing the gas are disagreeing with each other.
What P2138 means
In a drive-by-wire car, the accelerator pedal does not pull a cable. Instead, two or three sensors inside the pedal assembly tell the engine computer how far you are pressing it. In the SAE scheme, sensors D, E and F refer to the pedal, while A, B and C usually refer to the throttle body. P2138 sets when sensors D and E do not agree. RepairPal explains that when the computer detects a problem with these sensors or their circuit, it may limit the vehicle to 20 mph or less in limp home mode. That protects you from unintended acceleration but makes the car hard to drive. Common causes are a worn pedal sensor, a corroded or loose pedal connector, and damaged wiring under the dash. Water from a leak or wet shoes can reach the connector. KBB warns against driving because it can impair acceleration control. Shops graph both pedal sensor voltages while slowly pressing the pedal and check the wiring. A worn pedal sensor usually means a new pedal assembly.
Common symptoms
- Check engine light, often with a wrench or reduced power light
- Car stuck in reduced power (limp) mode
- Poor or no response to the gas pedal
- Rough or high idle
- Stalling in some cases
Most common causes
- Worn accelerator pedal position sensor
- Corroded or loose pedal connector
- Damaged wiring between the pedal and computer
- Moisture in the pedal connector from a leak or wet floor
- Throttle body problem on some vehicles
- Engine computer fault (rare)
What to check yourself first
Inspect the connector at the top of the gas pedal for corrosion or a loose fit. Check whether the carpet is wet from a leak. Make sure a floor mat is not interfering with the pedal.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | Checks the pedal connector and wiring, which often get wet or damaged. |
| Check engine light diagnosis at a shop | $125-$183 | Confirms whether the pedal sensor, wiring or throttle body is at fault. A worn pedal sensor is usually replaced as a complete pedal assembly. |
| Replace throttle body | $623-$766 | On some vehicles the fault is on the throttle body side instead. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P2135 Throttle/Pedal Position Sensor/Switch "A"/"B" Voltage Correlation
- P2101 Throttle Actuator "A" Control Motor Circuit Range/Performance
- P2119 Throttle Actuator "A" Control Throttle Body Range/Performance
- P0120 Throttle/Pedal Position Sensor/Switch "A" Circuit
- P0122 Throttle/Pedal Position Sensor/Switch "A" Circuit Low