They unlocked the car. But they couldn't drive off.
With a relay attack, thieves can unlock a keyless car without ever touching your key. LockCAR CAN-IMMO is the obstacle they meet next: without your PIN or paired device, the engine won’t start. An unlocked car doesn’t have to be a stolen car.
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- No monthly subscription
Watch: they got in. They didn’t drive off.
60 seconds: how a relay attack fools a keyless car, and what happens next when LockCAR CAN-IMMO is fitted.
The night, frame by frame
02:47. A keyless car on the driveway. 
The relay: the car thinks its key is beside it. 
Behind the wheel. The engine won’t start. 
No start, so they give up and run. 
LockCAR CAN-IMMO, 48 × 24 × 15 mm.
A relay attack, and where CAN-IMMO stops it
Keyless entry is built for convenience: the car opens when the key is close. A relay attack abuses exactly that.
They relay the signal
Two thieves work together. One device near your home picks up your keyless key’s signal, another near the car passes it on, and the car thinks the key is right beside it. Help Net Security reports this can take under 30 seconds.
The doors unlock
No broken glass, no damaged locks. They open the door and sit behind the wheel. Up to here, the car has been fooled.
The engine won’t start
With LockCAR CAN-IMMO fitted, the engine stays blocked until your PIN is entered or your paired device is present. The relayed key signal isn’t enough, so the car stays where it is.
The honest version: CAN-IMMO doesn’t stop a relay attack unlocking your doors. It stops what thieves came for, which is driving the car away.
Does an immobiliser stop keyless relay theft?
It stops the theft, not the break-in. A relay attack fools the keyless system into unlocking the car. LockCAR CAN-IMMO adds a separate check before the engine will start, and a relayed key signal can’t pass it on its own. Read the LockCAR CAN-IMMO guide.
What it stops
- Starting the engine with a relayed key signal
- Driving away with a copied or newly programmed key
- A thief finding it: no keypad, no LEDs, nothing on show
- Knocks, tilting and the car being moved going unnoticed, thanks to the shock sensor
What it doesn’t do
- Stop a relay attack unlocking the doors
- Protect valuables left inside the car
- Track the car: it isn’t a GPS tracker
- Stop the car being lifted onto a truck
What LockCAR CAN-IMMO adds to a keyless car
- PIN to start
- The engine stays blocked until the right code is entered, even if the doors are open and the key signal has been relayed.
- Hands-free option
- Pair a Bluetooth TAG, smartwatch, fitness band or smart ring. The PIN stays as a backup.
- Hidden fitting
- No keypad, no LEDs and no visible indicator, in a concealed, car-specific location.
- Shock sensor
- Notices impacts, tilting and unauthorised movement.
- Service mode
- Lets a mechanic or valet move the car without your PIN. Switch it off afterwards.
- No subscription
- Core protection needs no monthly fee. Firmware updates arrive through the app.
Technical specifications
| Model | LockCAR CAN-IMMO |
|---|---|
| Made in | United Kingdom |
| Supply voltage | 12–24 V DC (cars, vans and commercial vehicles) |
| Module size | 48 × 24 × 15 mm |
| Vehicle networks | CAN bus, LIN bus and ADC bus |
| Warranty | 12 months |
| Subscription | None required |
And you? You sleep soundly.
The film ends the way it should: the thieves gone, and the car still on the driveway in the morning.
That’s the point of an extra layer. Keyless entry stays as convenient as it was. It just stops being enough, on its own, for someone else to drive your car away. At 02:47 the doors may open, but the engine waits for you.
Check compatibility with LockCAR CAN-IMMO
Or just message us
Send us your car’s make, model and year, and we’ll tell you which protection fits it.
Fitted by our approved installers across the UK.
Cut the relay risk at home, too
- Use a signal-blocking pouchIt stops the key’s signal reaching a relay device. Test it: with the key inside, the car shouldn’t unlock.
- Keep keys away from doors and windowsThe deeper inside your home the key sits, the harder its signal is to pick up.
- Check whether keyless can be switched offSome cars let you turn keyless entry off in the settings. Your handbook or dealer can tell you.
- Lock the diagnostic portAn OBD lock covers the socket thieves use to program new keys. The RACV recommends one.
Questions about keyless relay theft
What is a relay attack on a keyless car?
Thieves use two devices to pass the signal between your keyless key and your car, so the car thinks the key is right beside it and unlocks. Help Net Security reports that a relay attack can take under 30 seconds.
Can LockCAR CAN-IMMO stop a relay attack?
It doesn't stop the doors being unlocked. It stops the drive-away: without your PIN or paired device, the engine stays blocked, so a relayed key signal isn't enough to start the car.
Can I still use keyless entry with CAN-IMMO fitted?
Yes. Keyless entry works as before. CAN-IMMO adds one step before the engine will start: enter your PIN, or have your paired device with you.
Is a signal-blocking pouch enough?
A pouch helps, and we recommend one, but it only works if the key goes back in it every time. CAN-IMMO still protects the car on the night the key is left on the hall table.
Will LockCAR CAN-IMMO fit my car?
LockCAR CAN-IMMO works with CAN bus, LIN bus and ADC bus vehicles. Search our finder, or send us your car's make, model and year, and we'll confirm compatibility.
What if a mechanic needs to move the car?
Service mode, set in the app, lets a mechanic or valet move the car without your PIN. Switch it off again when you collect the car.
Written by the LockCAR engineering team. We design and build our immobilisers in the UK and fit them through our approved installers. Meet the engineers. Last updated .
