VW GROUP DIAGNOSTICS & REPAIRS // 2026-10-28 // 2 min read
VW Group Keyless Entry Faults — "Key Not Detected" Explained
"Key not detected" on a VW, Audi, Škoda or SEAT is often a door or interior antenna fault rather than a flat fob. Here's the order to check things in, including the emergency start procedure.
"Key not detected" — what it means
VW Group's keyless system (KESSY on VW and Škoda, Audi Advanced Key, SEAT keyless) allows the car to be unlocked and started with the key in your pocket. When it fails, the cluster shows "Key not detected" or "No key in vehicle", and the start button may not respond.
This is a communication fault between the key, the antennas in the car and the immobiliser control unit — not necessarily a flat key battery.
First checks, in order
- Try the spare key. If the spare works, the fault is in your key (battery, or the key itself)
- Replace the key fob battery — CR2032 or CR2025, depending on model. A weak battery is the most common cause of intermittent detection
- Emergency start procedure — hold the key fob against the marked spot on the steering column (or the start button, on some models) and press start. If the car starts, the key's transponder is fine and the fault is in the detection antennas
- Check for water ingress — door handle sensors and the KESSY module are common water-damage points
The faults we actually find
- Door handle antennas — the capacitive sensors in the handles fail through wear and water; usually one door stops working first
- Interior antennas — the antennas in the cabin that locate the key for starting. A failed one causes intermittent no-start while unlocking still works
- KESSY control unit — water ingress or internal failure; diagnostics point here when multiple antennas drop out
- Key fob failure — dropped keys damage the PCB; the fob may work for unlocking but not starting
- Immobiliser/ELV faults — on older models the steering lock and immobiliser interlock can fail, which also prevents starting
- Wiring and connector corrosion — particularly in door looms and the tailgate
A note on key programming
Replacement keys and fobs must be programmed to the immobiliser with manufacturer-level equipment, and all keys must be present for some procedures. A key that is not correctly matched will unlock nothing and start nothing.
How we diagnose it
We read the KESSY and immobiliser control units, check which antennas are responding, and test the key's signal — then confirm the repair with a full lock, unlock and start cycle on every door. See advanced diagnostics and auto-electrical services for how we handle this at our Telford workshop.
Related reading
This article is general guidance for UK-market VW Group vehicles.