friends of the motor, I have spent some time investigating a way to find out if my car's control unit is reprogrammable, my car is a BMW Series3 323I M 98', 6 cylinders 170 hp, if it were, I am also looking for a way to do it, I know I could take to some specialized site, but this is a project that I want to carry out by myself with the help of a few.

2 Answers 2


The easiest way to figure out if your ECU is reprogrammable is to do an internet search. First you need to figure out what ECU your car uses, then you can ask the question if there are ways for it to be reprogrammed. Most vehicles ECUs are reprogrammable, it's just the matter of figuring out how it is done.

A cursory glance around the internet shows me your ECU is most likely an MS41 or MS42, which appear to be programmable. This may or may not be the correct one for your car. If you want to know for sure, find the ECU in your car and read the information which is directly on the ECU. You cannot go wrong by looking directly at what is in the vehicle to begin with.

You need to figure out what is your end goal. Are you reprogramming just to reprogram? Or are you trying to reprogram so as to add power or improve mileage? If just trying to learn the process of reprogramming, then I'd highly suggest you find some online courses (there are plenty) which can teach you about your specific ECU and application, what your approach to this might be, as well as an understanding of the equipment and software required to do the job.

To reprogram most OBDII vehicles ('96 and newer here in the States ... European vehicles may be different as they can have different OBD specifications) requires special equipment and software. You'll need a laptop with a dongle which can plug into the Data Link Connector (DLC ... also known as an OBDII port). With the proper software, you'd then read the "tune" which is in the vehicle, make the changes needed, then reprogram your ECU pushing the new parameters back to the ECU. Not only does this take specific tools and software to accomplish, it takes knowledge of how the ECU operates and of the many tables programmed into the ECU which allow the engine to function. Without the knowledge, you run the risk of destroying your ECU. It isn't something you play with and expect results not ending in catastrophe.

There are some tuning devices which just plug directly into the DLC, you press a button, and it uploads a new "tune" directly into the ECU. These types are VERY limited in what you can change. They have a canned tune which is very generic and can help in some cases, but in most, only provide a minimal amount of performance gain.

  • Hello, I was looking and indeed my ECU is a BMW MS42, I know what according to and how I can break the ECU, but I am lucky to have a colleague who has the same one from a broken car that he had..., and with that it will be the one I want to do tests with. For me I have spent days searching the internet for software and hardware that does not appear, could you recommend me one? Commented Oct 12, 2022 at 19:04
  • @DavidGonzalo - I'll suggest the following because it is free: romraider.com Commented Oct 13, 2022 at 20:12

I assume this is a MS42 ECU. If yes then there are several methods for tuning it. If you can do it yourself or not, I have no clue. It takes some specialized tools and knowledge in a few different things to be able to achieve it. If your starting from zero then it will be a long road.

Check out https://www.ms4x.net/index.php?title=Siemens_MS42 to get you started.

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