Computer question...
 

Hey everyone. Just have a quick question. Does anyone know if the ECU itself needs to be grounded or if anything attached to the ECU needs to be grounded to the car?

Thanks !

The ECU itself doesn't need to be grounded.
That is, the case of it, not the electronics inside. Who knows about them... ;)

Mine is sitting on a piece of carpet beside the KLR and alarm box on the passenger side. Not touching anything grounded at all, and my 951 runs just fine.

What is a KLR?

the computer that controls boost on a 951. talks to the DME if it gets a detonation signal from the knock sensor, among other things.

It's like the KGB except for cars. If knock happens, it gets rid of it.

What do the different numbers on the ECU mean?

For example mine says 944.618.121.02?

you need to look in the PET for this information. i think it is available on porsche's official web page.

basically the different years have different part numbers. some are interchangeable, some are not. they switched from 5V to 8V, i believe, in 1985.5. there are other differences as well.

I did a search ... can't find any information on the ECU in the PET. Can you give me a page number or section where I would find this information?

Also, What was the OEM for the ECU. Was it Bosch or Motronic? I am assuming Bosch.

bosch is the brand, motronic is their trademark. i'll see what i can find.

Thanks Nynor, I really appreciate it!

http://www.porsche.com/usa/accessoriesandservices/classic/classic-originalparts/originalparts-originalparts/

page 310. mainly lists the years for the different part numbers on the DME. is there a specific question you have?

I'm worried that the PO may have put in the wrong ECU because I've been having starting and running problems. I plan on replacing it because of this problem when I get the money. My ECU shows 944.618.121.02 and I'm driving a 1985.5 944 NA.

Thanks!

.02. could be. i think the .02 is for an early 944, which is 5V. is there someone that could loan you a DME for testing purposes?

found a link to ecu's: http://www.programainc.com/files/ProductList.xls
POR 924S 2.5, 944 85-87 944 618 121 02 Engine Control Unit

looks correct

Awesome link Earlr! This helps out a lot.

Looks like I can also use a 944.168.121.03 right?

I wonder if .03 is a better design.

sure, but the 02 is correct, it may not be functioning properly but it is the rught part number

Freaken sweeet. Thanks Earlr.

FWIW, the early's use the 12V AFM signal.
Early DME with late AFM = fried AFM.

The .02 number is fine. If your car runs most of the time, you have the correct DME, but something else is wrong.
Check the solder joints as advised over on Clarks.

right. i knew there was a voltage difference.

Zero10,

Yes, I recently discovered that if I pull the ECU out and set it on the passenger side carpet my car doesn't give me any troubles. Once I put the ECU back behind the floorboard it gives me starting and stalling problems. I am thinking it's a solder joint or a wire.

I was just wondering which computer number I should look for when replacing the ECU.