Aftermarket Immobiliser vs IMMOSTOP: What's the Difference?
If you've researched aftermarket car security, two names keep coming up: the aftermarket immobiliser and phone-based immobilisers like IMMOSTOP. Both are designed to stop the modern wave of keyless and relay theft without relying on your key — but they go about it in very different ways. This is an honest, side-by-side look so you can choose the right one for your car.
What an aftermarket immobiliser is
An aftermarket immobiliser is an aftermarket device that connects to your car's CAN-bus data network. Instead of a key fob, you disarm it by entering a secret PIN sequence using buttons the car already has — the steering-wheel controls, door buttons or gear selector. There's no extra tag to carry and, because it talks to the car's data network, installers can usually fit it without cutting wires. The trade-off is that you (and every driver) must remember and tap in the code before each journey, and because it operates over the data bus, it is — like any device — not completely immune to a determined electronic attack.
What IMMOSTOP is
IMMOSTOP holds the engine immobilised at two separate physical points and only releases them when your authorised phone is in range. It arms and disarms automatically as you come and go — no code to enter, nothing to remember — and runs in the background with the app closed. The cut is a physical interruption on low-risk circuits, and the trigger switches an earth (low-side) rather than feeding power to a relay coil, which is the harder method for a thief to defeat. A hands-free smart tag acts as a second key, and the system is installed by Autosecureshop, vehicle security specialists.
How each one stops the car
- aftermarket immobiliser: sends a block over the CAN bus so the engine won't start until the PIN is entered.
- IMMOSTOP: physically interrupts the engine at two points; there's no single data message or wire that releases it.
Both approaches defeat a relay attack, because neither is released by the key — a relayed or cloned fob is useless to a thief if the car still won't drive.
Can either be bypassed?
Here's the honest answer: no immobiliser is 100% un-bypassable, and you should be wary of anyone who claims otherwise. An aftermarket immobiliser works on the data bus, so the relevant risk is advanced CAN-bus attacks. IMMOSTOP uses a physical cut that can't be "talked past" over the bus, but like all security it's one strong layer rather than a magic wall. The point of either device is simple: make your car far more work than the car next to it, so the thief moves on.
Everyday use, cost and insurance
In daily use the difference is stark: an aftermarket immobiliser needs a PIN every drive; IMMOSTOP is automatic. Both are discreet and hidden. On price, get a quote per car — costs vary by vehicle and installer. On insurance, a quality immobiliser can reduce your theft risk and sometimes your premium, but always confirm with your insurer first (see our guide on whether an immobiliser lowers insurance).
Which should you choose?
If you never want to carry anything and don't mind tapping a code before every journey, an aftermarket immobiliser suits you. If you'd rather it be completely automatic, use a physical cut that can't be addressed over the data bus, and add or remove drivers from an app with no shared PIN, IMMOSTOP is the better fit. Owners also like that IMMOSTOP boards are owner-locked with one-time recovery codes, so being locked out is never a dead end.
Automatic, phone-released, dual-point protection — no code to remember. See how IMMOSTOP works →
More on vehicle security
- What makes a good car immobiliser?
- What is a relay attack — and how do you stop it?
- How IMMOSTOP works
- Compare IMMOSTOP vs trackers, steering locks & aftermarket immobilisers
- Order IMMOSTOP (£349 all-in, fitted)
- Autosecureshop — vehicle security specialists
Frequently asked questions
Can an aftermarket immobiliser be bypassed?
No immobiliser is completely un-bypassable. An aftermarket immobiliser works over the car's CAN-bus data network, so the realistic risk is advanced CAN-bus attacks. It remains a strong deterrent, but it is one layer of security rather than a guarantee. IMMOSTOP uses a physical engine cut that cannot be released by a data-bus message.
Do I have to enter a PIN every time with IMMOSTOP?
No. Unlike an aftermarket immobiliser, IMMOSTOP arms and disarms automatically when your authorised phone is in range, so there is no code to enter and nothing to remember. A hands-free smart tag can act as a second key.
Will an immobiliser lower my car insurance?
It can. A good immobiliser reduces theft risk and some insurers reward that with a lower premium, but it varies by provider. Always confirm with your insurer before buying, and ask what security they require.
Which is better for a keyless car — an aftermarket immobiliser or IMMOSTOP?
Both defeat relay and keyless theft because neither is released by the key. IMMOSTOP is the more convenient choice because it is automatic and uses a physical cut, while an aftermarket immobiliser requires a PIN on every drive and operates over the data bus.