Throttle/Pedal Position Sensor/Switch "A" / "B" Voltage Correlation
The Powertrain Control Module (PCM) detected that the voltage signals from Throttle Position Sensor (TPS) or Accelerator Pedal Position (APP) sensors 'A' and 'B' do not correlate with each other. This means the two redundant sensors are sending conflicting information about the actual position of the throttle valve or gas pedal.
This code is highly urgent because conflicting throttle position data forces the vehicle into a fail-safe 'limp mode' to prevent unintended acceleration. It poses a significant safety risk if power is suddenly lost while driving in traffic.
Common symptoms
- Check Engine Light illumination
- Vehicle enters 'limp mode' with severely reduced engine power
- Poor, delayed, or no acceleration when pressing the gas pedal
- Rough idling, surging, or stalling
- Engine revs unexpectedly or hesitates during operation
Likely causes
- Defective Throttle Position Sensor (TPS) or Accelerator Pedal Position (APP) sensor
- Damaged, corroded, or loose wiring and connectors in the TPS or APP circuits
- Dirty or carbon-fouled electronic throttle body causing the plate to stick
- Faulty electronic throttle body assembly (internal motor or gear failure)
- Poor electrical ground connection in the sensor circuit
- Powertrain Control Module (PCM) failure or requiring a software update (rare)
What to check before replacing parts
Visually inspect the wiring harnesses and connectors at the throttle body and accelerator pedal.
Look for: Look for frayed wires, corrosion, water intrusion, or loose pins that could cause intermittent signal loss or high resistance.
Monitor TPS and APP sensor live data using an advanced scan tool.
Look for: Observe the voltage sweeps of sensors A and B while slowly pressing the pedal; look for dropouts, spikes, or voltages that do not correctly correlate (often one sweeps 0-5V while the other sweeps 5-0V, or one is exactly half the voltage of the other).
Inspect the electronic throttle body for carbon buildup.
Look for: Look for excessive carbon deposits around the throttle plate and bore that might cause the valve to bind, preventing it from reaching the commanded position.
Test the sensor reference voltage and ground circuits with a multimeter.
Look for: Verify a steady 5-volt reference signal from the PCM and a solid ground at the sensor connectors with the key on, engine off.
Perform a continuity and resistance test on the signal wires between the sensors and the PCM.
Look for: Look for open circuits, shorts to ground, shorts to voltage, or higher than normal resistance indicating a wiring fault.
This page explains the generic P2135 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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