Hi:

does anyone have any experience on interfacing electrically with the engine control computer, for the purpose of reading sensors (door switches, trunk switch, etc.) ? I have a microcontroller which I want to use for my own security improvments on my new 2013 Accord, and my preferred approach is to somehow tap into engine control computer using serial communication.

Has anyone attempted this or know any links to refer me to ?
thanks,
bb

 

Moved post to correct forum. Don't post in DIY for help.

good luck

 

wow. helluva project. as an EE I appreciate your enthusiasm.

is it possible? sure.
will you ever be able to get a good schematic of the ECM? not likely.

you'll also be messing with the impedance seen by the ECM which will likely cause issues. your biggest challenge will be getting the information you need from Honda. writing code and making connections is fairly straightforward once you know what you're connecting to.

in the end, a $250 unit properly installed will be faster, cheaper, easier, and more reliable.

 

kha:

I'm an EE myself, dabbled with software/microcontrollers before. Good to know you have EE experience as well, always good to have someone to consult with.

Ambitious plan, yes. For short term, I'll have to tap into wiring harness to access signals I need, this is why I'm after service manual schematics. Long term, a serial interface into ECM is best approach, but not the easy one, as you point out. I will start simple and go from there.

 

analog I/O are easy to program. i have some DSP's left over from college that I know could make decent security systems. a serial interface requires that the ECM already has the capability to share the information you need. you don't want to get into the ECM programming, you just want to be able to read information that is already provided as an output.

after a while of thinking about making my own, i spent $250 on an Autopage RS900LCD and i'm plenty happy. one of these days i'm going to program one of the aux outputs to control my garage door so my key fob can open the door as i'm walking down the drive. it's as simple as setting the momentary delay in the alarm and wiring in parallel with the factory button (using Honda home link). modern alarms have a wealth of features and programming options to keep any EE satisfied.

note that if you do something to the ECM programming that is an issue, your dealer isn't likely to repair or reprogram, they will just charge your a few grand for a new one.

of course, solder every connection - no scotchlocks.