P1772
Load Signal Stuck On.
- Volkswagen
- Powertrain
- Manufacturer code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 1
- Defined byThe manufacturer
- 7
- AreaTransmission
- 72
- FaultThe specific fault in that area
What it means
On Volkswagen, P1772 means the transmission control unit is receiving an engine load signal that is stuck in the 'on' state and does not change with throttle or engine load. The transmission control unit uses this signal to set shift points and line pressure, so it compares the signal with other inputs such as throttle position, engine speed and vehicle speed. If it stays fixed when it should vary, the code is set. How the signal is delivered (a dedicated wire or a data bus message) depends on the model and gearbox.
Symptoms
- Gearbox warning light on or transmission in limp-home mode
- Harsh, delayed or flared gear changes
- Gearbox stuck in one gear or shifting at fixed, unsuitable points
- Poor or inconsistent acceleration
- Possible engine management warning light alongside the gearbox fault
- Fault returns after being cleared
Possible causes
- Wiring fault in the load signal circuit between the engine control unit and transmission control unit (short to power, chafing or corrosion)likely
- Poor connection or corroded pins at the engine control unit, transmission control unit or inline connectorslikely
- Faulty throttle position or accelerator pedal sensor giving the engine control unit a wrong load valuepossible
- Engine control unit fault or incorrect output of the load signalpossible
- Data bus communication fault between control units, on models where the load signal is sent as a bus messagepossible
- Internal fault in the transmission control unitrare
- Outdated control unit software on certain models, where a manufacturer update is known to address itrare
How to diagnose
- Read all stored codes in both the engine and transmission control units and note any related throttle, pedal or communication faults.
- Check freeze frame data and live data: compare the load signal and throttle position with engine speed and see whether the load value changes when you open the throttle.
- Visually inspect the wiring and connectors between the engine and transmission control units for chafing, water ingress, corrosion and bent or pushed-back pins.
- Check the wiring diagram for your model to see whether the load signal is a dedicated wire or a bus message, and follow the correct test route.
- With the ignition off and connectors disconnected, test the signal wire for continuity and for short to power or earth.
- Check the throttle position and accelerator pedal sensor readings for smooth, plausible changes through the full range.
- Check the battery condition and the power and earth supplies to both control units.
- Clear the codes and road test, watching whether the fault returns and under what conditions.
How to fix
- Repair or replace damaged wiring or the affected section of the load signal circuit.
- Clean, repair or replace corroded or loose connectors and terminals.
- Replace a faulty throttle position sensor or accelerator pedal sensor.
- Repair the data bus fault if the load signal is sent over the bus.
- Replace or repair the engine or transmission control unit only after wiring and sensors are proven good, and code or adapt it as required.
- Apply a manufacturer software update if one is available for the vehicle and addresses this fault.
Can I keep driving?
The car can usually be driven carefully for a short time, but the gearbox may shift harshly or stay in limp mode, which can increase wear. Have it diagnosed soon and avoid heavy loads or long journeys until it is fixed.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.