YOUR CAR
CAN BE STOLEN
in under 60 seconds with no alarm triggered
CAN bus vs relay immobiliser — the difference that costs £800
Ghost uses your car’s CAN bus. LockCar uses a physical relay. Both prevent relay attacks — but the risk profile, warranty implications, and price are completely different.
This is the most important technical distinction in the UK immobiliser market. CAN bus and relay-based approaches both stop the engine — but they do it in fundamentally different ways, with fundamentally different consequences for your ECU, your warranty, and your bank balance.
The core technical difference
A CAN bus immobiliser connects a new device to your car’s Controller Area Network — the communication backbone that all your vehicle’s electronic control units use to talk to each other. It works by monitoring the network for a specific button sequence (the PIN), and only sending the necessary ECU command to allow the engine to start when that sequence is detected.
A relay-based immobiliser places a physical switch in an engine circuit — typically the fuel pump or starter relay. When the switch is open (armed), the circuit is broken and the engine cannot start. When closed (disarmed), the car behaves exactly normally. There is no ECU interaction of any kind.
The relay immobiliser doesn’t know anything about your car’s electronics. It doesn’t need to. It just breaks a wire — with a 20-amp relay that can be opened and closed electronically. The car’s ECU, the key signal, the CAN bus — none of this matters. A broken fuel pump circuit is a broken fuel pump circuit.
| Factor | CAN bus (Ghost) | Relay (LockCar) |
|---|---|---|
| ECU contact | Yes — writes to CAN bus | None |
| ECU interference risk | Documented — real-world cases | Zero |
| BMW warranty | Voided (BMW confirmed) | Not affected |
| Volvo warranty | Issues reported | Not affected |
| Disarming | PIN button sequence | Proximity tag hands-free |
| Lockout risk | Yes — forgotten PIN | No — tag backup included |
| GPS/tracking | Not included | Available (ONE Plus) |
| App control | No | Full app — alerts, status, remote |
| Fitted price | £450–600 | £300–450 |
| EV safety | Caution — EV CAN bus complex | Safe — 12V aux only |
Real-world ECU interference cases
CAN bus interference from aftermarket devices is not theoretical. UK automotive forums contain documented owner accounts of ECU faults, dashboard warning lights, limp mode, and failed MOTs traced back to CAN bus immobiliser installations. The faults don’t occur on every vehicle — but they occur on enough to represent a genuine risk worth evaluating.
When CAN bus is the right choice
Ghost and CAN bus systems have a larger installer network, greater brand recognition, and Thatcham approval. If your insurer has specifically required a Thatcham-approved CAN bus immobiliser — and it does happen for some high-risk vehicles — Ghost may be the correct product despite these risks. The key is to go into that decision with eyes open, not because Ghost is the only option you know about.
LockCar IC3ST — the relay choice
Zero ECU contact. Proximity tag. App control. Lower fitted price. Warranty safe on all makes. Same relay attack protection as Ghost without the CAN bus risk.
IC3ST details → Full Ghost comparison →from £300 fitted
