P2135 on GMC: How to Diagnose & Fix
Throttle/Pedal Position Sensor Voltage Correlation
1 GMC model · 1 documented issue · $250-$650 repair
P2135 on GMC by model: symptoms, diagnosis and fix
First-generation Terrains (2010-2017) are prone to a sudden 'Reduced Engine Power' warning caused by a failing electronic throttle body. Carbon and grime build up inside the bore and the internal throttle position sensor (TPS) fails or reads erratically, causing the ECM to enter a limp/reduced-power mode that limits the vehicle to very low speed. This is a widely reported failure on the naturally aspirated 2.4L four-cylinder and 3.6L V6 engines and frequently appears alongside a 'Service StabiliTrak' message. The most commonly cited trouble code is P2135 (throttle/pedal position sensor voltage correlation). No NHTSA recall covers the throttle body; it is addressed through non-recall repair.
Common Symptoms
- 'Reduced Engine Power' message on dash
- Sudden loss of acceleration / limp mode
- Check engine light
- 'Service StabiliTrak' message
- Rough idle or stalling
How to Fix
Clean the throttle body if carbon buildup is the cause; if the throttle position sensor has failed the electronic throttle body assembly is replaced as a unit and the idle/throttle relearn procedure is performed.
Sources for this issue (2)
P2135 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P2135 mean on a GMC?
P2135 stands for "Throttle/Pedal Position Sensor Voltage Correlation." P2135 means the powertrain computer detected that the two throttle position (TP) or accelerator pedal position sensors disagree with each other. Drive-by-wire systems use redundant sensors so the PCM can cross-check the throttle or pedal reading for safety; if the two signals don't correlate within an expected range, this code sets. As a fail-safe, the vehicle often enters a reduced-power 'limp' mode, causing sluggish acceleration, a stuck or hesitant throttle, and a warning light. Because it affects throttle control, it should be addressed promptly. On GMC it is documented across 1 model: Terrain.
What are the most common causes of P2135?
The most common causes of P2135 are: Faulty throttle position sensor / throttle body assembly, Faulty accelerator pedal position sensor, Damaged wiring or connectors at the throttle body or pedal, Corroded or loose connector terminals, Poor ground or reference voltage problem, Carbon buildup binding the electronic throttle plate, Failed PCM (rare). The specific cause varies by vehicle.
How much does it cost to fix P2135 on a GMC?
Published repair estimates on GMC range from $250 to $650 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.