OBD-II Code P2138 — What It Means & How to Fix It

What Does This Error Mean?

P2138 means the Throttle/Pedal Position Sensor D/E Voltage Correlation fault is present. This code is specifically about the accelerator pedal position sensor — not the throttle body. The pedal sensor has two signal channels (D and E) that must agree with each other. When those two signals diverge, P2138 is set. Symptoms are similar to P2135 — limp mode, reduced power, unresponsive pedal.

Affected Models

Common in Chevrolet Silverado, Tahoe, and Suburban
Common in GMC Sierra, Yukon, and Canyon
Common in Chevrolet TrailBlazer and Envoy
Seen in Dodge Ram and Jeep Grand Cherokee with drive-by-wire pedals

Common Causes

Faulty accelerator pedal position (APP) sensor — one of the two internal sensor channels has failed
Moisture or corrosion in the APP sensor connector causing one signal to read incorrectly
Damaged wiring on one of the two APP sensor signal circuits
APP sensor connector partially unplugged — losing contact on one signal channel
PCM input circuit fault reading one APP channel incorrectly

How to Fix It

Locate the accelerator pedal connector under the dashboard. Inspect it for moisture, corrosion, or loose connection.

The dual-channel APP sensor connector is a common weak point. Reconnecting it firmly resolves many P2138 cases.
Use a scan tool with live data to observe both APP sensor signal voltages simultaneously while pressing the pedal slowly.

Both channels should rise smoothly together from idle to full pedal. A flat line on one channel indicates that channel is faulty.
Inspect the wiring harness from the pedal to the PCM firewall pass-through for chafing or pinching.

Wiring can be pinched under the carpet or against sheet metal, especially after interior work has been done.
Apply dielectric grease to the APP connector contacts and reconnect firmly. Clear the code and test drive.

If the fault was moisture-related, dielectric grease prevents recurrence without needing to replace any parts.
Replace the accelerator pedal assembly if one APP sensor channel consistently reads out of range or flat.

The dual APP sensors are integrated into the pedal unit — they are not individually serviceable.

When to Call a Professional

Accelerator pedal assembly replacement is $50 to $200 in parts. Labor is 30 to 60 minutes — total shop cost is $100 to $300. Always inspect the wiring harness carefully before replacing the pedal assembly. Professional diagnosis with a live data scanner saves time and money.

Frequently Asked Questions

What is the difference between P2135 and P2138?

P2135 is a voltage correlation fault in the throttle body position sensors (sensors A and B on the throttle body). P2138 is a voltage correlation fault in the accelerator pedal position sensors (sensors D and E on the gas pedal). Both result in similar symptoms — limp mode and reduced power — but affect different components.

Can both P2135 and P2138 appear at the same time?

Yes, they can. Some PCM or wiring faults affect both the throttle body and pedal sensor simultaneously. However, it is more common for only one to be present at a time. Diagnose each code's root cause separately.

After replacing the pedal assembly, do I need any programming?

Most accelerator pedal assemblies are plug-and-play — no programming is needed after replacement. Just connect the new pedal, clear the codes, and test drive. If the code returns after replacement, the issue is in the wiring harness or PCM, not the pedal.