P2135 Code on Chevy Silverado: Throttle/Pedal Position Sensor Voltage Correlation

Chevy Silverado Reduced Engine Power P2135 Diagnosis

Quick Answer: What is P2135?

On a Chevy Silverado, the P2135 code means the computer is seeing conflicting voltage signals between the Throttle Position Sensor (TPS) on the engine and the Accelerator Pedal Position (APP) sensor inside the cab. To prevent the truck from accelerating uncontrollably, the computer triggers the "Reduced Engine Power" mode. The most common fix is replacing the electronic throttle body assembly.

Severity: HIGH. When this code triggers, your Silverado goes into "Limp Mode." You will lose almost all acceleration capability, making it very dangerous to drive on the highway. Pull over safely as soon as the "Reduced Engine Power" message appears.

1. Common Symptoms in a Chevy Silverado

The symptoms of a P2135 are impossible to ignore. You will experience:

"Reduced Engine Power" Message: Displayed clearly on the Driver Information Center (DIC) on your dashboard.
Severe Loss of Power: The truck will suddenly refuse to accelerate past 20 or 30 MPH, no matter how hard you press the gas pedal.
Stalling: The engine may completely shut off while driving or coming to a stop.
Check Engine Light: Illuminates solidly, often accompanied by the Traction Control/StabiliTrak light.

2. Most Likely Causes (Ranked by Probability)

GM trucks (Chevy Silverado, GMC Sierra, Chevy Tahoe) have well-documented issues with their electronic throttle systems:

Defective Throttle Body Sensor (60% of cases): The internal contacts inside the Throttle Position Sensor (which is built into the throttle body) wear out and send erratic signals.
Poor Electrical Connection (20% of cases): GM issued a technical bulletin regarding "fretting corrosion" (microscopic rust) on the wiring harness connector that plugs into the throttle body.
Dirty Throttle Body (10% of cases): Excessive carbon buildup preventing the throttle plate from closing correctly.
Faulty Accelerator Pedal Sensor (10% of cases): The sensor attached to the gas pedal inside the cabin is failing.

3. Step-by-Step Diagnostic and Fix

Step A: Inspect and Clean the Connector

Before buying expensive parts, open the hood and locate the throttle body (at the front of the intake manifold). Unplug the electrical connector. Look closely at the metal pins inside. If they look dull, dirty, or slightly corroded, clean them with electrical contact cleaner and apply a tiny amount of dielectric grease. Reconnect it, clear the code, and see if the truck drives normally.

Step B: Replace the Throttle Body

On modern Silverados, the Throttle Position Sensor is riveted inside the throttle body. You cannot replace just the sensor; you must replace the entire throttle body assembly. Fortunately, it is a very easy DIY job. It usually requires removing the air intake tube and taking out four 10mm bolts. After replacing it, the truck will need a few minutes to "relearn" the idle.

4. Estimated Repair Costs

Dealerships often charge a premium for this repair, but doing it yourself can save hundreds of dollars:

Repair Type	Estimated Cost (USD)
Clean Throttle Body & Connections (DIY)	$15 (Cost of cleaners)
Replace Accelerator Pedal Sensor Assembly	$100 - $180 (Parts only)
Replace Throttle Body Assembly (DIY)	$150 - $250
Replace Throttle Body (Mechanic / Dealership)	$400 - $700+