Fuel & air metering · Powertrain · generic (SAE-defined)
P2138: Throttle/Pedal Position Sensor/Switch "D"/"E" Voltage Correlation
P2138 means the two accelerator pedal position sensor signals, D and E, do not agree with each other, so the computer cannot confirm how far the pedal is pressed.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P2138 sets
The accelerator pedal assembly contains two accelerator pedal position (APP) sensors that report pedal travel independently. The powertrain control module (PCM) checks that the two signals track each other, and when they diverge beyond a set amount, P2138 sets and engine output is restricted. The allowed difference varies by manufacturer.
Common causes of P2138
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Worn or failed accelerator pedal position sensor
- Corroded or loose pedal connector
- Chafed or broken wiring under the dash
- Shared 5-volt reference or ground fault
- Liquid spilled into the pedal sensor area
- PCM fault (rare)
P2138 symptoms
- Check engine light and/or reduced power warning
- Limp mode or idle-only operation
- Delayed or inconsistent pedal response
- Possible surging when the pedal is held steady
How P2138 is diagnosed
- Scan all codes and review freeze frame data.
- Inspect the pedal connector and harness for damage or corrosion.
- Graph both pedal sensor signals while slowly pressing and releasing the pedal; look for dropouts or non-linear spots.
- Check reference voltage, ground, and voltage drop at the pedal connector.
- Wiggle-test wiring while monitoring the signals.
- Replace the pedal assembly if wiring tests pass.
Typical fixes for P2138
- Replace the accelerator pedal assembly
- Repair pedal wiring or the connector
- Correct reference voltage or ground issues
- Clear codes and perform any required relearn
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P2138 FAQ
What does code P2138 mean?
P2138 means the two accelerator pedal position sensor signals, D and E, do not agree with each other, so the computer cannot confirm how far the pedal is pressed. The standard definition is "Throttle/Pedal Position Sensor/Switch "D"/"E" Voltage Correlation."
Can I drive with a P2138 code?
Only with caution and only to a repair shop. The vehicle typically limits power or idles only, which can leave it unable to keep up with traffic.
Is P2138 usually the pedal itself?
The pedal sensor assembly is a common cause, but connector and wiring faults under the dash should be ruled out first.
Why does my car only idle with P2138?
Without a trustworthy pedal reading, the computer may keep the engine near idle to avoid unintended acceleration.
Keep researching
Engine guides by brand (known issues, specs)
More fuel & air metering codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.