Engine management systems or as they are more commonly named ECU's are very expensive to replace. You can however buy second hand, reconditioned and remanufactured units at a fraction of the cost of new replacements.

ECU's are sealed components with no serviceable or replaceable parts inside. They can however be repaired and reprogrammed and performance increases can also be made using various testing, computer and electrical equipment. There main functions include ignition spark, fuel management, engine speed and engine temperature. So if your ECU is not functioning correctly you can experience a multitude of problems.

Some of the most common are as follows:

• Fuel consumption is greatly higher than normal making travel very costly.
• Fuel regulation is way to low and vehicle keeps stalling with problems starting again.
• Vehicle simply wont start.

 
Another thing to consider when replacing your ECU is the age of your vehicle. If it is before 1994 then you should have no problems simply changing over the unit so long as the model, engine size and serial numbers all match. After 1994 ECU's are immobilised and will only work in your vehicle. With most units the codes can be wiped and once the new unit is fitted to your vehicle the unit can 'learn' new codes. With some units it is also possible to transfer existing codes to a new unit.

Immobilisation was introduced as an anti-theft system to stop vehicles from being hot wired. If you don't have the original keys the engine just wont start as they are coded to the vehicles ECU making theft more difficult.

 
So it is possible to replace an ECU for greatly reduced cost. Some units can cost in excess of over 1000 pounds which in some cases exceeds the value of the vehicle and just isn't financially sensible.

We hope this guide is useful and informative and have more on the way. As and when we are asked other relevant questions we will update this guide and add new ones to help as best we can.

Thanks for reading and happy motoring.