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DTC codes / Volkswagen codes / P1634

P1634 · VolkswagenAccelerator Pedal Position Sensor 2 Signal Too High

P1634 on Volkswagen vehicles means the engine control module (ECM) has detected a signal voltage from accelerator pedal position sensor 2 that is higher than the expected range for the current pedal position. Sensor 2 is the redundant tracking sensor in the drive-by-wire pedal assembly, and the ECM compares its voltage against sensor 1 to verify the driver's requested throttle input.

SystemPowertrain
Code typeVolkswagen specific
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • The electronic throttle control (EPC) warning light or check engine light illuminates on the dashboard
  • The engine may enter limp mode, limiting power and engine speed to a fast idle
  • The accelerator pedal may feel unresponsive or the engine may not rev when pressed
  • A sudden loss of power or hesitation during acceleration
  • Often no symptoms besides the warning light, especially if the fault is intermittent

Common causes, most likely first

  1. Faulty accelerator pedal position sensor 2 inside the pedal assembly
  2. Worn or corroded electrical connector at the accelerator pedal sensor
  3. Damaged or chafed wiring between the pedal sensor and the ECM
  4. Water ingress or contamination in the pedal sensor connector or housing
  5. Poor ground connection for the pedal sensor circuit
  6. Internal ECM fault affecting the sensor reference voltage or signal processing

How to diagnose and fix it

  1. Scan all modules for fault codes and record freeze-frame data to confirm the condition under which P1634 sets
  2. Inspect the accelerator pedal sensor connector and wiring for corrosion, water intrusion, or physical damage
  3. Back-probe the sensor 2 signal wire at the pedal and compare voltage with the ECM data stream through the full pedal travel
  4. Check the sensor reference voltage and ground circuits for voltage drops or opens
  5. If wiring and connectors are good, replace the accelerator pedal assembly with the integrated sensors
  6. Clear codes and perform a throttle adaptation or pedal learn procedure with a suitable scan tool
  7. Road test the vehicle through several drive cycles to verify the repair and confirm no pending codes return

Why P1634 is often a wiring fault

  • The accelerator pedal sensor 2 signal is a low-voltage analog output, so a small amount of corrosion or a poor ground can push the voltage above the expected range and set P1634 without the pedal being mechanically faulty.
  • Many technicians replace the pedal assembly first, but a thorough back-probe of the signal wire at the ECM connector often reveals a chafed harness or a bad splice that is the real cause.
  • P1634 can be set by a weak or failing battery or charging system, because low system voltage can distort the sensor reference voltage and cause the ECM to see an out-of-range signal.
  • On some Volkswagen models, the pedal sensor connector sits low in the footwell and can be contaminated by spilled liquids or floor cleaning, leading to intermittent high-signal faults.
  • A throttle body adaptation that has not been performed after battery replacement or ECM work can cause pedal correlation codes, so always complete the learn procedure before condemning parts.

Can I keep driving with P1634?

The vehicle may enter limp mode with limited power, so avoid highway driving and heavy traffic until the fault is repaired. If the pedal response is erratic or the engine will not rev, stop driving and have the vehicle towed to a workshop.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Volkswagen vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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