Fitting a used control unit, what does it take?
When a control unit fails, a new one from the manufacturer can cost more than the car is worth. A used unit from a breaker is then a sensible option, but it rarely works just by plugging it in.
Why a used unit does not just work
In a modern car the control units recognise each other. A used unit holds another car's data:
- VIN. The unit knows which car it belongs to.
- Immobiliser data. The engine control unit and immobiliser are paired. Wrong pair, and the car will not start.
- Equipment coding. The unit is coded for another car's equipment, such as the gearbox, lights or comfort features.
- Software version. It may differ from the other units, which causes fault codes.
What adaptation means
Adaptation programs the right car's data into the unit, pairs the immobiliser and codes the equipment. Sometimes the software needs updating or the unit needs a full reprogram. The scope depends on the make, model and unit.
Before you buy
- Check the part number. A unit that looks the same is not necessarily the same. Software and hardware versions decide.
- Ask the seller which car the unit came from. The VIN and model year help.
- Ask us before buying. Send the part number and the car details, and we will tell you whether adaptation is possible and what it takes.
Programming is billed at €100/h, and coding is priced per job and control unit. See full pricing or read more about control unit services.