OBD-II Code P2135 — What It Means & How to Fix It

What Does This Error Mean?

P2135 means the Throttle/Pedal Position Sensor A/B Voltage Correlation fault is detected. Modern drive-by-wire throttle bodies have two position sensors that must agree within a tight tolerance. When the two TPS signals diverge beyond the allowed range, P2135 is stored. The PCM cannot trust throttle position data when the sensors disagree. Symptoms include reduced power, limp mode, stalling, and unresponsive acceleration.

Affected Models

Very common in Chevrolet Silverado, Tahoe, and Suburban
Common in GMC Sierra, Yukon, and Envoy
Common in Chevrolet Impala, Malibu, and Cobalt
Also seen in Toyota, Ford, and Chrysler vehicles with dual-TPS throttle bodies

Common Causes

Faulty throttle body — one of the two internal TPS sensors has failed or drifted out of spec
Carbon buildup on the throttle plate causing erratic, inconsistent position readings
Damaged wiring or connector to the throttle body affecting one of the two sensor signals
Corrosion in the throttle body connector creating resistance on one sensor circuit
PCM fault causing it to misread one of the two sensor channels

How to Fix It

Inspect and clean the throttle body thoroughly — carbon buildup on the throttle plate is the most common cause of P2135 on GM trucks.

Use throttle body cleaner only. Work the throttle plate by hand while cleaning to dislodge stubborn deposits.
Inspect the throttle body electrical connector for corrosion, bent pins, or loose fit. Disconnect and reconnect it firmly.

Corrosion on a single pin can affect one of the two TPS signals, causing them to diverge.
After cleaning, perform the throttle body idle relearn procedure for your specific vehicle.

On GM vehicles, turning the key to RUN without starting (for 30 seconds) allows the PCM to recalibrate the throttle position baseline.
Use a scan tool with live data to observe both TPS signal voltages simultaneously during throttle movement.

Both sensors should track together smoothly from idle to WOT. Any divergence points to either a sensor fault or a sticky throttle.
Replace the throttle body as a complete assembly if one sensor is drifting out of range or the code returns after cleaning.

Individual TPS sensors inside the throttle body are not serviceable on most vehicles — the full throttle body must be replaced.

When to Call a Professional

Throttle body cleaning costs $50 to $100 at a shop. Throttle body replacement is $100 to $350 for most GM vehicles. Always perform a throttle relearn after replacement — failure to do so causes recurring codes. PCM replacement (if at fault) is $200 to $600.

Frequently Asked Questions

Why does the throttle body have two position sensors?

Redundancy is the reason. A single sensor failure could cause the PCM to misjudge throttle position and potentially cause unintended acceleration. By using two sensors that mirror each other, the PCM can detect if either one is wrong. This is a safety feature required by modern vehicle safety standards.

Is P2135 a common code on GM trucks?

Very common — especially on GM trucks and SUVs with the 4.8L, 5.3L, and 6.0L V8 engines. Carbon buildup on the throttle plate is a well-known issue on these engines. Regular throttle body cleaning every 30,000 to 50,000 miles is recommended as a preventive measure.

Can I clean the throttle body myself?

Yes — it is one of the more DIY-friendly tasks. Remove the air intake tube, spray throttle body cleaner on a lint-free cloth, and wipe the plate and bore. Do NOT spray cleaner directly into the engine while it is running. Always perform the idle relearn after cleaning on electronic throttle systems.