Motronic

[Todd Knighton]

Chris Denzler wrote:
> 
> Thanks for the advice to all those who offered it.
> 
> dave said:
> 
> > "hardware" method... definetly learn some code. Number ONE step is to
> > find the checksum.. the program wont run or allow you to use a scan tool
> > if you change bytes without addressing the checksum issue.
> 
> The only system I've ever explored previously was the older (pre-93) Weber
> Marelli ECU, as used on Ducati and Moto Guzzi motorcycles and (I've heard)
> Alfo Romeo 6 cylinder cars.  There wasn't any checksum problem at all, you
> could whack in any changes to the EPROM at will.  Is the Motronic checksum
> just a loop that adds all the EPROM bytes together and compares that value
> to the checksum value?  (don't answer if that is sensitive information, I'm
> merely curious and not working on a Motronic system)
> 
>                                       - Chris

Chris,
	Not quite all the bytes, but you've got the general Idea.  If they
added up all the bytes then put in the check sum, the check sum would
change, so they've got to put the check sum outside the area they're
working with.

Todd Knighton
Protomotive Engineering