Early E30, Late M20. Motronic Help Please!

[ProRes]

I've searched a bunch, but couldnt find much pertaining to my situation and it would be great if i could get some things cleared up.

I have a '87 325is that i am swapping a late model (1990 i believe) m20b25 into. I have an ECU with a dinan chip that came with, and was used with the m20 i am installing.

If the late model m20 and ECU are motronic 1.3, then do i need to worry about the C104 connection in the glovebox? Can i just leave it and forget about it, or do i need to do some wiring?

If my '87 was motronic 1.1 then the swap to 1.3 is all in the ECU correct? meaning that my C101 hookup on the body will be plug and play to the late model m20 C101? Do i still need to cut the wire to pin 20 on the C101 because its a ground on my cars body?

Thanks

[jlevie]

The necessity of dealing with C104 has everything to do with the production dates of the car and engine harness. In this case the car requires that C104 mate with the engine harness or that the car's wiring be modified to route those signals through C101 if using a later production engine harness.

[ProRes]

Ok thank you for the help. What is the better/cleaner of the two options? Does it matter? I would like to just Splice the C104 connection off the old harness into the late model harness... Seems like that would be a cleaner install than running wires to the C101. Do you have a preference?