Car won't start?
Immobiliser light
flashing?
Mobile immobiliser fault diagnostics and repair, at your driveway or roadside across South & West Wales — finding out why your car won't recognise its own key.
What the immobiliser does, and why it locks you out
Your immobiliser reads a transponder chip in your key before the ECU will allow the engine to start — a legal, standard anti-theft feature on virtually every car built in the last 25 years.
When that handshake between key, immobiliser and ECU breaks down — a failing ring aerial, a corroded connector, a weak key battery, or a fault in the module itself — the car refuses to start, even with the correct key in hand.
We connect directly to the vehicle's immobiliser system, read live communication data between the key and the modules, and identify exactly where that handshake is failing.
Not every no-start means the same thing
Faulty Ring Aerial
The coil around the ignition barrel that reads your key's chip can fail or work loose, breaking the handshake.
Weak or Failing Key Battery
A low battery in a proximity or remote key can mimic a serious immobiliser fault — often the simplest fix of all.
Water or Corrosion Damage
Damp ignition barrels or corroded connectors disrupt the signal between key and immobiliser module.
Relay & Wiring Faults
A faulty starter relay or damaged wiring loom can prevent the immobiliser from releasing the engine, even with a good key.
Battery Drain & Resets
A recent flat battery or disconnection can occasionally leave the immobiliser out of sync until it's properly re-learned.
Aftermarket Alarm Conflicts
Poorly installed aftermarket alarms or trackers can interfere with the factory immobiliser circuit.
What we'll ask you to bring
Because immobiliser work can involve resetting or reprogramming a car's security system, we ask for proof of ownership and photo ID before starting any work.
This protects you as much as it protects us, and it's a quick check rather than a hurdle — we'll tell you exactly what to have ready when you book.
V5C Logbook
Showing you as the registered keeper, or documentation confirming your right to authorise the work.
Photo ID
A driving licence or passport matching the name on the vehicle documents.
Any Keys You Have
Even a key that isn't working helps us diagnose whether the fault is with the key or the vehicle's system.
Four steps to a car that starts again
Book Your Slot
Tell us what's happening — dash light, no-crank, or crank-but-no-start — and we'll get a visit booked in.
We Come To You
Home, work or roadside — anywhere across South & West Wales.
Verify & Diagnose
Ownership and ID checked, then live communication between key, immobiliser and ECU is tested.
Repair & Test
Fault repaired where possible on-site, and the car tested to confirm it starts reliably.
Book a DiagnosticOther faults sorted in the same visit
Key Coding
Lost, spare or replacement keys coded to your vehicle on-site.
Full Fault Diagnosis
A complete system scan if there's an underlying electrical issue beyond the immobiliser itself.
Mileage Correction
Recalibrating displayed mileage after a cluster, ECU or gearbox replacement.
Performance & Economy Tuning
Once you're back on the road, ask us about getting more from the car — power or mpg.
A no-start is stressful. We keep it simple.
Whether it's a flat key battery or a genuine module fault, we work through the immobiliser system methodically so you're not left guessing, or paying to replace parts that were never the problem.
Genuinely Mobile
We bring the full diagnostic kit to your driveway or roadside — no towing to a garage unless it's genuinely needed.
All Major Manufacturers
From everyday runarounds to keyless entry systems, we cover the vast majority of makes and models.
Security-Conscious Process
Proof of ownership and ID checked every time — proper protection, not just a quick reset.
Straight-Talking Diagnosis
A clear explanation of what's actually wrong before any work starts, with no pressure to over-spend.
From drivers stranded by a car that wouldn't start
"Immobiliser light flashing, key wouldn't work at all. Turned out to be a corroded ring aerial — fixed on the drive."
"Nearly bought a new key before WCH found it was just a flat key battery. Saved me a lot of money."
"After a flat battery the car wouldn't recognise the key at all. Re-synced properly and started first time."
Mobile across South & West Wales
If you're within reach of these areas, we'll come to you. Based further afield? Get in touch — we regularly travel beyond our core patch for the right job.
