// What fails
Later Mercedes platforms use FBS4 drive authorisation, where the engine ECU, ignition/drive authorisation data and related modules must agree before the car will start. A used ECU that looks physically identical can still be useless if the immobiliser data and coding are not handled correctly.
We work with CRD3 and related Mercedes ECU families at bench level: reading, backing up, cloning where possible, matching donor units and checking communication before the part goes back to the vehicle. The aim is simple — keep the original car data intact and avoid an expensive dealer-only parts chain where a specialist route is possible.
Symptoms we see every week
- Mercedes no-start after ECU failure, water damage or previous programming attempt
- CRD3 ECU replacement needed but the donor unit is not matched to the vehicle
- Drive authorisation / start enable problems after module replacement
- Original ECU data needs cloning or recovery before a donor unit can be used
- Workshop or garage needs a specialist bench programming route before refitting the ECU
Our process
- DiagnoseThe fault is confirmed with proper diagnostics and board inspection before any work is quoted.
- RepairComponent-level repair on your original unit — coding, keys and adaptations preserved.
- Bench testThe repaired unit is proven on the bench under realistic conditions before it goes back.
- WarrantyWork is covered by our workshop warranty, with terms confirmed in writing on your quote.
FBS4 and CRD3 jobs are assessed case by case. We identify the ECU family and part number, back up readable data, confirm whether cloning or matching is possible, and only then quote the safest route. If the data cannot be recovered, we say so before wasting your money.
Pricing
FBS4 / CRD3 pricing depends on the ECU, donor availability, data condition and required programming route. Send the Mercedes model, year, ECU part number, symptoms and photos of the label for a firm quote.
Frequently asked questions
Can you clone every Mercedes FBS4 ECU?
No. Anyone promising that without seeing the ECU, part number and data condition is guessing. Some units can be cloned or matched cleanly, others need a different route, and some damaged ECUs cannot be read. We check first and quote honestly.
What information do you need before quoting?
Send the model, year, fault symptoms, ECU part number, photos of the ECU label, and whether you have the original ECU, donor ECU, keys/EZS or other related modules. More context means a faster, more accurate answer.
Is this only for Mercedes CRD3 diesel ECUs?
CRD3 is a common Mercedes diesel ECU family we see, but the service is broader: FBS4 drive authorisation, ECU cloning, module matching and bench checks on supported Mercedes ECU systems.
Can garages send units by post?
Yes. Many FBS4 / CRD3 jobs are handled as postal bench work for garages and owners. Contact us first so we can confirm exactly what modules and donor parts should be sent.