Worn or contaminated accelerator pedal position sensor 2 track inside the pedal assembly, the most common cause on higher-mileage Volkswagens; Corroded, backed-out, or chafed wiring in the pedal sensor harness connector or the loom between the pedal and the ECM; Water ingress into the pedal connector or footwell wiring from a leaking windscreen scuttle drain or blocked plenum; Poor ground or reference voltage supply shared by the pedal sensors, often due to a loose engine-bay ground strap; Failed or failing accelerator pedal assembly as a complete unit after internal sensor wear; Rarely, an internal fault in the ECM driver circuit for sensor 2 after a voltage spike or jump-start event

DTC codes / Volkswagen codes / P1633

P1633 · VolkswagenAccelerator Pedal Position Sensor 2 Signal Too Low

Q: What does code P1633 mean?

Accelerator Pedal Position Sensor 2 Signal Too Low. P1633 on a Volkswagen means the engine control module (ECM) has detected that the signal voltage from accelerator pedal position sensor 2 is lower than the expected range for the current pedal position. Sensor 2 is the redundant track inside the drive-by-wire pedal assembly, and the ECM compares it against sensor 1 to verify the driver's requested throttle; a persistently low signal on track 2 triggers this code and usually forces a reduced-power limp mode.

P1633 on a Volkswagen means the engine control module (ECM) has detected that the signal voltage from accelerator pedal position sensor 2 is lower than the expected range for the current pedal position. Sensor 2 is the redundant track inside the drive-by-wire pedal assembly, and the ECM compares it against sensor 1 to verify the driver's requested throttle; a persistently low signal on track 2 triggers this code and usually forces a reduced-power limp mode.

SystemPowertrain

Code typeVolkswagen specific

SeverityMedium

Fix difficultyIntermediate

AreaComputer and output circuits

Symptoms you may notice

The electronic throttle warning light or check engine light illuminates on the dashboard
The engine enters limp mode with severely reduced power and a throttle that responds sluggishly or not at all
The accelerator pedal may feel dead or have a delayed, uneven response when pressed
A message such as 'Engine fault workshop' or 'EPC' appears in the instrument cluster display
Often no symptoms besides the warning light if the fault is intermittent and sensor 1 still provides a plausible signal
Occasional rough idle or stalling when the ECM cannot reconcile the two pedal signals

Common causes, most likely first

Worn or contaminated accelerator pedal position sensor 2 track inside the pedal assembly, the most common cause on higher-mileage Volkswagens
Corroded, backed-out, or chafed wiring in the pedal sensor harness connector or the loom between the pedal and the ECM
Water ingress into the pedal connector or footwell wiring from a leaking windscreen scuttle drain or blocked plenum
Poor ground or reference voltage supply shared by the pedal sensors, often due to a loose engine-bay ground strap
Failed or failing accelerator pedal assembly as a complete unit after internal sensor wear
Rarely, an internal fault in the ECM driver circuit for sensor 2 after a voltage spike or jump-start event

How to diagnose and fix it

Scan all modules with a Volkswagen-compatible scan tool and record the freeze-frame data and live accelerator pedal sensor 1 and sensor 2 voltages at rest and through the full pedal travel
Visually inspect the pedal connector and harness for corrosion, water intrusion, chafed insulation, and loose terminals, then clean and reseat the connector
Back-probe sensor 2 at the pedal connector and verify its signal voltage rises smoothly from roughly 0.4 to 4.5 volts as the pedal is pressed, comparing it against sensor 1
Check the sensor ground and 5-volt reference at the pedal connector with a multimeter under load to rule out a shared supply or ground fault
If the signal is missing or erratic at the pedal but the supply and ground are good, replace the accelerator pedal assembly and clear the code
If the pedal signal is correct at the connector but the ECM still logs P1633, perform a continuity and resistance test on the signal wire back to the ECM and repair any open or high-resistance section
After repair, clear the fault memory, perform a throttle adaptation or basic setting with the scan tool, and road-test through the full pedal range to confirm the code does not return

What P1633 hides about the pedal circuit

Many technicians replace the accelerator pedal only to find the real fault is a corroded connector pin or a chafed wire behind the pedal, so always back-probe the signal before condemning the assembly.
A weak or intermittent ground shared with other sensors can pull sensor 2 low without any pedal wear at all, and this is easily missed if only the pedal is tested in isolation.
Water leaking from a blocked scuttle drain into the driver footwell is a known Volkswagen cause of pedal sensor corrosion, so check for damp carpet and green crust on the pins.
P1633 can be stored intermittently by a low battery or a voltage spike during a jump-start, so clear the code and recheck before authorizing parts if the fault is not repeatable.
On some Volkswagens the pedal sensor signal passes through an intermediate connector in the footwell or bulkhead, and a loose terminal there mimics a failed pedal perfectly.

Can I keep driving with P1633?

The car is usually drivable only in limp mode with severely reduced power, which makes merging and hill climbs unsafe, so limit driving to a short trip to a workshop. If the pedal response is dead or erratic, do not drive on public roads and arrange a tow instead.

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.