Saturday, December 4, 2010

So you want to hack your ECU. Where do you start?

I've been reverse engineering automotive engine control units (ECUs) since 2001.  Recently, an acquaintance encouraged me to write a blog about it.  At first, I wasn't sure if anyone would really be interested about the internal details of ECUs, but then I thought, why not.  So if you're reading this, I assume you are the curious type, are interested in cars and electronics, and aren't afraid to use a soldering iron.  I plan to write about how I got into ECU hacking, the basics of how to do it, such as what tools you need, and some of what I've learned along the way.  So let's start from the beginning.

I wasn't always interested in cars.  In fact, growing up I never really thought of them as anything more than a form of transportation until one singular experience changed everything for me - playing Gran Turismo.  I know, it sounds kind of silly, and it is, but that's really the reason why I got excited about cars, and why, in 2001, I bought a used Honda 1991 CRX Si (which had seen better days), bought a used Jackson Racing supercharger, which I installed myself to save money, and, finally, decided to crack open the CRX's ECU to see if I could hack it myself, because the only other option at the time was to pay someone else about $1000 to do it.  So, what started out mainly as an attempt to go fast cheaply has turned into a long-term hobby, and since that time, I have had almost as much fun working on my cars and hacking their ECUs as I've had driving them.

In 2001, the conventional wisdom was that Honda ECUs couldn't be hacked, except by the few commercial outfits that were charging an arm and a leg for their services.  But hey, if they could do it, why couldn't I?  I decided to open up my ECU and see.  What I found was a pleasant surprise:  My CRX's ECU was powered by an 8051 microcontroller and used a standard 28-pin EPROM.  It'd be hard to come up with a more common combination of parts.  There were plenty of 8051 code disassemblers that could be downloaded for free, as well as datasheets.  I was fortunate enough to have access to an EPROM programmer, so all I had to was desolder the EPROM, read it and disassemble it.  If you're interested, you can read more about it here:

Since the CRX, I've owned a supercharged '93 Civic Si, a supercharged '94 Integra GS-R and now a 2001 Mazda Miata, and I've hacked the ECU in each one.  I've also gone from having no kids to 4, so I don't have as much free time to devote to this as I used to, but I will try to post regularly about what you need to do to hack your own ECU, from the ground up, including what hardware and software tools you'll need and where to find them.  Stay tuned.


  1. I have recently desired to learn more about this subject and this is exactly what I'm looking for! I look forward to read the rest of your entries.

  2. Have you done any work on GM ECM's?

  3. No, sorry, I stick with makes I actually own. I believe there's a pretty active community of GM ECU hackers, though.