Search for a "ghost alarm" and you will find thousands of results — but the Autowatch Ghost II is not an alarm at all. It is a silent immobiliser that stops your engine starting without a secret PIN. This guide explains the difference between alarms and immobilisers, why traditional car alarms no longer stop modern thieves, and why insurers for Range Rover, BMW and other high-value vehicles now prefer the Ghost.
Ghost II blocks engine start with a secret PIN — no noise, no warning.
Sirens rarely stop thieves; relay attacks bypass them entirely.
TASSA-verified and accepted by most premium-vehicle insurers.
Ignores the original key — defeats relay and cloning attacks.
Vehicle security splits into two jobs: deterrence (scare thieves away) and prevention (stop the car being driven). Alarms and immobilisers each target one of these — and understanding the difference is the key to choosing the right protection.
Car alarm (deterrence) — A traditional alarm detects intrusion through door, bonnet, boot or motion sensors. When triggered, it sounds a loud siren and flashes the hazard lights to attract attention. Alarms rely on bystanders or owners hearing the noise and reacting. They do not stop the engine starting, and most modern thefts (relay, cloning, OBD) bypass the alarm entirely by presenting what the car thinks is a genuine key.
Ghost II immobiliser (prevention) — The Ghost is installed deep inside the CAN-bus and requires a secret PIN sequence entered on dashboard or steering-wheel buttons before the engine will start. There is no siren, no flashing lights and no key fob to clone. A thief with your key, a relay device or a cloned signal will still be unable to drive the car. It is completely silent and invisible — and that is exactly why it works.
Here is how the two systems compare across the features that matter most for high-value vehicles:
| Feature | Ghost II Immobiliser | Traditional Car Alarm |
|---|---|---|
| Primary purpose | Prevent engine starting | Deter break-ins with noise |
| How it works | Secret PIN via dashboard buttons | Sensors trigger siren + lights |
| Stops relay attacks | ✓ Key is irrelevant | — Bypassed by relay device |
| Stops key cloning | ✓ PIN required regardless | — Cloned key disarms alarm |
| Audible deterrent | — Completely silent | ✓ Siren + hazard lights |
| Detects break-ins | — Engine-start only | ✓ Door, glass, motion sensors |
| Ongoing fees | None | None |
| Insurance approval | ✓ TASSA-verified, widely accepted | ~ Thatcham Cat 1 only |
| Best for | Range Rover, BMW, keyless cars | Smash-and-grab deterrence |
| Typical install cost | From £499 fitted | £300–£600 fitted |
Car alarms were designed for an era of broken windows and hot-wired ignitions. Today's most prolific theft methods bypass them in seconds — without ever triggering a sensor.
This is why insurers for Range Rover, Land Rover Defender, BMW X-series and Mercedes G-Wagon now commonly specify a Ghost II immobiliser or equivalent CAN-bus immobiliser as a condition of theft cover, regardless of whether the car has a factory alarm.
Most modern cars already have a factory alarm. The real question is what to add on top. Here is our straightforward guidance:
Factory alarm only: The default for most cars. Provides break-in deterrence but does not stop relay, cloning or OBD attacks. Leaves keyless-entry vehicles exposed to the most common theft methods of 2025.
Ghost II only: The strongest single upgrade for keyless-entry vehicles. Silent, no ongoing fees, defeats relay and cloning attacks. Works alongside the factory alarm — you keep break-in deterrence and add drive-away prevention.
Ghost II + Thatcham S5 Tracker (recommended): The gold standard for Range Rover, BMW, Mercedes and other high-value vehicles. The Ghost stops the car being driven; the S5 ensures recovery if it is loaded onto a recovery truck. This is what most premium-vehicle insurers now require for full theft cover. See our Ghost vs S5 tracker guide for a deeper comparison.
Still unsure? WhatsApp us your vehicle registration and insurer name. We will confirm exactly what your policy requires and quote the right protection — no upsell, just the security you need.
No. The Autowatch Ghost II is a silent immobiliser, not an alarm. It does not make any noise, flash lights or sound a siren. Instead, it blocks the engine from starting unless a secret PIN sequence is entered using buttons already on your dashboard or steering wheel. Thieves get no warning — the car simply will not move.
A car alarm is a deterrent: it detects break-ins or movement and sounds a siren to scare thieves and alert bystanders. An immobiliser like the Ghost II is a preventer: it stops the engine from starting in the first place. Alarms are reactive; immobilisers are proactive. Modern thieves often ignore alarms — they just need a few seconds with a relay device — but a Ghost-protected car cannot be driven away at all.
Traditional alarms are largely ineffective against today's most common theft methods. Relay attacks, key cloning and OBD port hacks all bypass standard alarms entirely, because the car thinks the genuine key is present. Sirens are also widely ignored in busy areas. That is why insurers for high-value vehicles increasingly require a Ghost II immobiliser instead of, or in addition to, the factory alarm.
Insurers care about prevention, not noise. A Ghost II immobiliser stops over 99% of attempted thefts because the engine simply will not start without the PIN — there is nothing to bypass with a relay, cloned key or OBD attack. Audible alarms do not stop the car being driven. For Range Rover, BMW X-series, Mercedes G-Wagon and other premium vehicles, many insurers now require a Ghost or equivalent CAN-bus immobiliser as a condition of theft cover.
Yes, and this is the strongest setup for high-value vehicles. The factory alarm provides an audible deterrent against break-ins (smash-and-grab, catalytic converter theft), while the Ghost II prevents the car being driven away. Pair both with a Thatcham S5 tracker for layered protection: deterrence, prevention and recovery in one stack.
They do different jobs. A Thatcham Category 1 alarm combines an alarm with a basic immobiliser, but it is still triggered by the original key — so relay attacks and key cloning defeat it. The Ghost II is a TASSA-verified aftermarket immobiliser that ignores the key entirely and requires a secret PIN. For keyless-entry vehicles, the Ghost is the stronger protection.
A professionally installed Autowatch Ghost II starts from £499 fitted, with no ongoing fees. Aftermarket Thatcham alarms typically cost £300–£600 fitted but offer far less protection against modern theft methods. Given the Ghost prevents over 99% of attempted thefts and is recognised by most insurers, it is widely considered the better value for high-value vehicles.
WhatsApp us your vehicle reg and insurer. We will confirm the right protection — Ghost II, S5 tracker, or both.
