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.

Severity4/5 High

Can I drive?⚠ 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.

DIY

$20–$150

Shop

$150–$700

Difficulty

intermediate

What It Means

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.

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

Common Causes

1. Faulty accelerator pedal position (APP) sensor assemblyhigh

2. Damaged wiring, loose connector, or poor terminal contact in the pedal or throttle control circuithigh

3. Throttle position sensor (TPS) fault or throttle body issue affecting signal correlationmedium

4. Corrosion, moisture intrusion, or damaged harness causing intermittent signal lossmedium

5. PCM internal fault or software calibration issuelow

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.