P2135 Throttle Sensor Error: Causes, Symptoms, and Repair Solutions

P2135: Throttle Position Sensor “A”/“B” Voltage Correlation

The P2135 code indicates that the engine control module (ECM) has detected a mismatch between the voltage signals of Throttle Position Sensor (TPS) A and TPS B (image below). These dual sensors work together to monitor throttle angle in modern cars’ drive-by-wire systems, ensuring smooth engine response and, more importantly, preventing unintended acceleration. When the two signals don’t align within the expected correlation range, the ECM triggers the P2135 code, shuts down throttle authority, and may put the vehicle into limp mode for safety.

Dodge Ram throttle position sensor TPSAmazon

You’ll see this fault frequently across many brands, as this is a generic diagnostic trouble code (DTC), so the P2135 code on Chevy models means the same as P2135 on Nissan, Ford, Toyota, and any other models using electronically controlled throttle bodies, and which run on the OBD-II diagnostic standard used since 1996. Let’s look at how to fix code P2135 on your car.

What the P2135 Code Means

Most modern engines no longer use a physical cable between the gas pedal and the throttle body; instead, the ECM receives signals from:

• TPS A – the primary throttle position sensor
• TPS B – the redundant sensor for safety verification
• Accelerator Pedal Position (APP) sensors

The ECM constantly compares the signals from TPS A and TPS B. When their voltages disagree—whether due to a wiring issue, failing sensor, or mechanical throttle body problem—the ECM assumes that throttle control is no longer reliable.

To prevent unsafe acceleration, the ECM may:

• Limit engine revs
• Disable throttle movement
• Reduce the engine power (limp mode)
• Turn on the Check Engine Light (CEL)

Because discrepancies can indicate unsafe operation, P2135 is considered a high-priority code.

Common Causes of the P2135 Engine Code

Here are the most frequent issues responsible for P2135 throttle position sensor correlation faults:

1. A failed throttle body (very common). Many vehicles use integrated TPS sensors built into the throttle body, and when the internal sensors fail, the entire throttle body has to be replaced.
2. A sticking or dirty throttle plate. Carbon buildup can cause the plate to bind or move inconsistently, leading to mismatched sensor readings.
3. A faulty Throttle Position Sensor (TPS). If your vehicle has replaceable TPS sensors, either the A or B sensor may have failed.
4. Damaged wiring or connectors. Even small resistance changes can throw off sensor correlation. Look for:

• Corroded terminals
• Broken wires
• Loose connectors
• Moisture intrusion

1. A bad Accelerator Pedal Position (APP) sensor (below). Though the APP sensor isn’t the direct cause of the P2135 code, it can confuse throttle calculations and contribute to correlation issues.
2. A faulty ECM (rare). If the ECM misinterprets sensor data, it may trigger false throttle correlation errors.

Ram accelerator pedal position sensor APPSAmazon

Depending on how severe the voltage discrepancy is, you may experience one or more of the following symptoms:

• The Check Engine Light
• Poor throttle response
• An unsteady or high idle
• Engine stumbling or hesitation
• Reduced engine power and/or activation of limp mode
• The engine won’t accelerate past low RPM
• A sudden loss of throttle while driving (safety mode)

Most drivers notice the engine becomes unresponsive or sluggish, especially when pressing the gas pedal.

How to Diagnose the P2135 Code

Professional diagnosis typically includes to:

1. Scan for related throttle error codes. Codes like P0121, P0222, P2138, and P2101 may accompany P2135 and help narrow the cause.
2. Inspect the throttle body (image below). Check for:

• Heavy carbon buildup
• A sticking throttle plate
• Dirt around the bore
• Physical damage

1. Inspect the wiring and connectors. Broken wires are very common, especially on GM trucks and SUVs, which could trigger P2135 on Chevy and GMC models. Focus on:

• The throttle body harness
• The APP sensor connector
• The ECM connector
• Shared grounds

1. Test the TPS A and TPS B voltage. Any hesitation, mismatch, or drop-out confirms the fault. Using a multimeter, slowly open and close the throttle. The voltage must increase smoothly. Both sensors must track each other consistently.
2. Test the accelerator pedal position sensor. APP sensors also provide redundant signals, and mismatches here can impact throttle correlation.
3. Check the ECM’s operation (if all else checks out). This is only done after all mechanical and electrical causes are eliminated.

Common Repairs for the P2135 Code

RepairNotesReplace the throttle bodyOften the most common fix on GM, Nissan, Ford, and ToyotaClean the throttle bodyRemoves carbon buildup that can cause stickingReplace the TPS sensor(s)On models where TPS is not integratedRepair wiring or connectorsFix breaks, corrosion, or loose/damaged pinsReplace the accelerator pedal position sensorIf the APP signals don’t correlatePerform a throttle body relearn procedureRequired after some repairsReplace the ECMRare, and only if confirmed faulty

Always clear codes and perform a drive cycle after repairs. If the P1000 code appears, the drive cycle wasn’t long enough.

Electronic throttle body for GMAmazon

FAQs

Q: How to reset the gas pedal sensor?

A: Most vehicles require either an ECM idle/throttle relearn or a manual pedal reset procedure, often involving key-on/key-off sequences. Your vehicle’s service manual will list the correct steps.

Q: How much does it cost to fix code P2135?

A: Typical repair costs:

• Throttle body replacement: $250–$650
• TPS replacement: $80–$200
• APP sensor replacement: $150–$300
• Wiring repair: $50–$150

Q: Can a bad throttle body cause P2135?

A: Yes; in fact, it’s the #1 cause. Internal TPS sensors often fail before the throttle body’s motor or gears do.

Q: How do you fix throttle position correlation?

A: Fixes include:

• Cleaning or replacing the throttle body
• Repairing the wiring
• Replacing the TPS or APP sensors
• Performing a throttle relearn procedure

Final Thoughts

The P2135 code is a serious drive-by-wire fault that affects throttle accuracy and safety. While the vehicle may still run, limp mode and power loss make continued driving inconvenient and potentially turn you into a hazard in traffic. Fortunately, the root cause is usually straightforward, with the throttle body or TPS sensors being the most common failures.

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