Thanks for pointing that out, although I already knew that it controls the EHA on the Fuel Distributor and the idle valve only.
I didn't want to explain all the details of what I've tested because I didn't want to bother everyone to death, but I should have done it to makes things more clear. I apologize for that.
To make the story short, I've followed the procedures on the MB 201 service manuals to check the different signals ( current variations ) that goes to the EHA on certain conditions ( RPMs, temp, O2 signal, etc ) and the MB diagrams end up with the "Replace Control Unit" box after some of the test.
Now, as I said before, since I have a friend with generic electronic test equipment, he offered me to test the unit. I know he doesn't have the internal schematics of the unit ( nobody does except Bosh ) and he won't be able to perform a complete test, but he offered me to test the micro controller which is the brain of box. He can only do that if he know what's the architecture which is what I'm trying to find out.
Maybe someone in the performance chip business knows as they have to modify some of the values of the fuel/advance maps of their chips, and to do that, you usually have to know the processor architecture to understand how the program runs on the box and how the values on the maps are used to signal the actuators, EHA, injectors, idle valve, coils, etc, etc. At least, the good tuners have to know this.
As I said, I know the correct procedure would be replace the unit, as the MB manual says, but since the car belongs to a friend, I was trying to save him some money and also learn something about electronic and software that runs on the box.
I whish I could find the diagrams of the unit, I know Bosh doesn't give away this, but it would very useful. Anyway it's an old, old technology, so there isn't any competitive advantage that Bosh should be afraid of giving out.
Sorry if my previous post caused any confusion.
87 Euro 190E 2.5-16
91 SportEvo E30 M3