Faults With the BMW Engine Control Unit


The Engine Control Unit (ECU) is an essential part of any vehicle; in effect it is the brain of the car, enabling the vehicle to perform a wide range of functions. These range from controlling the fuel and air mixture to controlling the ignition timing and maximizing the performance and fuel economy of the vehicle.

Many modern ECU’s are programmable. This means they can be adjusted, using specialized software, to improve performance; particularly when an aftermarket engine part has been fitted.

However, the ECU relies on a multitude of sensors located around the engine, should any one of these fail they can seriously affect the ability of the vehicle; possible even making it impossible to drive.


A common fault with the BMW ECU is shown via the following symptoms:

  • It is possible to crank the engine but the car will simply not start; sensor faults can often cause ragged performance but an ECU problem can prevent it from even starting.
  • The check engine light is on constantly, although the car may appear to drive normally.

The Cause

If your vehicle displays the above symptoms it is highly likely that there is a problem with the ECU; this problem is usually classed as an electrical problem inside the ECU. It is very difficult to take apart an ECU and trace a fault and this is not something your average home mechanic could do.

The Solution

There are several solutions to this problem:

  1. Take your vehicle, or have it towed to your local BMW mechanic and ask them to look at the issue. A new ECU is very expensive; it will cost over $1,000. It will then need to be fitted into the vehicle and coded to the car.
  2. Locate a second hand ECU from a junk yard or parts dealer. The part can be disconnected and unbolted from the car very easily. However, it is highly likely that the replacement ECU will have the same fault. In addition the ECU will need to be coded to match the car. Coding is a security feature as it is not possible to control the immobilizer and alarm without the ECU and the vehicle having matching codes.
  3. There are a few specialists who will be able to trace a fault within the ECU down, repair it and ensure the coding to the vehicle does not get altered. The best option is to send the entire ECU to Programainc.com; they will be able to repair or rebuild your ECU and return it to you with the same programming code still present in the ECU. This will ensure your car can communicate with the ECU and that it will start.

The choice is yours!

The third option is likely to be the fastest option as well; with the least amount of hassle. This is something that will, probably, be very important when you can’t afford to be without your wheels.

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