P2138
Accelerator Pedal Position Sensor Correlation Fault
The car's computer is getting conflicting signals from the accelerator pedal sensors. It cannot tell how far you are pressing the pedal, so it may reduce engine power or put the car in limp mode.
- SEV
- 4/5
- DRIVE
- CAUTION
- DIY
- $20–$150
- SHOP
- $150–$700
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Faulty accelerator pedal position (APP) sensor assembly
- Damaged wiring, loose connector, or poor terminal contact in the pedal or throttle control circuit
- Throttle position sensor (TPS) fault or throttle body issue affecting signal correlation
Typical repair cost
DIY usually runs $20–$150. Typical shop repair lands around $150–$700, depending on the root cause.
01 / Definition
P2138 indicates a correlation problem between accelerator pedal position sensor signals, usually APP sensor 1 and sensor 2. The PCM expects both signals to change in a specific relationship; if they do not, it sets this code and may restrict throttle operation to protect the engine and drivability.
02 / Drive status
With caution. You may be able to move the vehicle, but power can be limited without warning. Avoid highway driving and get it diagnosed as soon as possible.
03 / Symptoms
- Reduced engine power
- Limp mode
- Delayed or no throttle response
- Check engine light on
- Rough or inconsistent acceleration
- Engine may idle normally but not respond well to the pedal
04 / Causes
| 1 | Faulty accelerator pedal position (APP) sensor assembly | high |
|---|---|---|
| 2 | Damaged wiring, loose connector, or poor terminal contact in the pedal or throttle control circuit | high |
| 3 | Throttle position sensor (TPS) fault or throttle body issue affecting signal correlation | medium |
| 4 | Corrosion, moisture intrusion, or damaged harness causing intermittent signal loss | medium |
| 5 | PCM internal fault or software calibration issue | low |
05 / Diagnostic sequence
- 01Scan for all stored and pending codes and note any related throttle or pedal sensor codes.
- 02Inspect the accelerator pedal connector and wiring for damage, looseness, corrosion, or water intrusion.
- 03Check live data for both APP sensor signals and confirm they rise smoothly and stay in the expected range.
- 04Inspect throttle body connector, wiring, and TPS data for correlation issues.
- 05Test power, ground, and reference voltage at the pedal assembly and throttle body circuits.
- 06If wiring checks pass, follow manufacturer tests for APP sensor replacement or PCM software update/relearn.
- 07Clear codes and verify throttle response with a road test after repairs.
06 / Repairs
| 1 | Repair loose, corroded, or damaged wiring and connector terminals in the pedal or throttle circuit | $20–$150 |
|---|---|---|
| 2 | Clean or replace the accelerator pedal position sensor assembly if signal values are out of range | $80–$350 |
| 3 | Inspect and service the throttle body or throttle position sensor if correlation remains incorrect | $100–$450 |
| 4 | Update PCM software and perform required relearn procedures | $80–$200 |
| 5 | Replace the PCM only after all other tests confirm an internal module fault | $400–$1,200 |
MFG / Manufacturer notes
These supplements add make-specific diagnostic framing. Pages without full matrix backing or lane approval stay guarded and canonicalize back here until they are explicitly approved for indexing.
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Audi P2138
Expansion-candidate noindex child page
07 / Related codes
08 / FAQ
Can a bad battery or charging problem cause P2138?
Yes. Low system voltage or unstable power can affect sensor signals and trigger throttle correlation faults.
Will replacing the throttle body fix P2138?
Sometimes, but not always. The pedal assembly and wiring are more common causes, so diagnosis should come first.
Does P2138 mean the gas pedal is bad?
Often yes, but the problem can also be wiring, the throttle body, or the PCM.
Will the car go into limp mode with P2138?
It can. Many vehicles reduce engine power when the pedal sensor signals do not match.
09 / Source and method
- DATA BASIS
- OBD-II REFERENCE + OBD2.HELP
- METHOD
- STATIC VALIDATION
- SAFETY
- INFORMATIONAL
This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.
Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.
Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.