H2

I understand that S4 ECU computers are numbered from 928.618.123.10 up to 928.618.123.30. In view of the differing numbers, are they truly interchangeable from year to year as implied by listings? I'm looking for a spare to carry around with me in my '88 S4 5-speed and don't wish to buy the wrong one.

H2

Garth S

AFAIK, all S4 LH units are compatable, including GT and GTS: to specifically tailor a LH to a model year, the eprom/chip from the desired year must be inserted ..... ie - a '90 S4 or GT unit will work in your '88 - but will be more specifically matched if the eprom from the '88 LH is swapped in.
I've swapped some of these around when playing with various S4's - the changes are not earth shattering. BTW, the '87 units do not have the Hammer diagnostic link ... if that is important to you.

H2

Garth,

Where can one obtain the proper eprom from?

Thanks for the information.

H2

the flyin' scotsman

John Speake can blast some proms for you; thats where I got my GT chips.

TheoJ

The ecu's are interchangeable, true. Be aware that it does make sense to have the right software inside. The manual and automatic, as an example. have differences like idle RPM. The automatic likes a lower rpm when standing still in D. The fuel mapping is a bit different. And so on.

More info on my website.
regards,

John Speake

Garth is 100% correct. The EPROM binary files are available on Chris Ford's website .......

http://www.928s4.com/lh/lh_homepage.htm

Anyone with an EPROM programmer can blow am EPROM for you.

Garth S

H2,
You already have the correct chip in your '88 LH - just swap it over to whatever spare LH you source when and if req'd due to death of your current unit: it's only an extra 5-10 min. to do when the module is removed

H2

Garth....why didn't I think of that!???? OK...don't answer that. Great idea. I'm just looking for an emergency spare to carry and changing out an eprom would be easy.

Harvey

the flyin' scotsman

H2............I toyed with same and decided that a refurbed brain in the car and using the old as spare was a better choice IMHO.

We could debate this and all other potentail failures to death; I personally prefer to replace before they fail..............you decide where the break point is.

H2

Malcom,

That's a better idea. But you still carry a spare. I'd like to buy another LH so i could do that. Good idea. Thanks.

H2

Jim Reay

After replacing a fuse (remember my interior light woes) my 928 started okay, but then ran real rough. Spent what seemed like a lifetime trying to figure out what I had done, and was almost in despiar. Was the night before my son's wedding, and had promised the car for their Honeymoon. I could hear a click as the car switched modes, and discovered the red & green LEDs. I must have disturbed the connector, as a bit of a wriggle stopped the Red LED lighting up. It seems the unit needd very good contact, and a poor earth can cause problems. I have sprayed with the connector, and contacts to the unit with cleaner, and has been good since.

Jim Reay
1991 928 S4