[s-cars] ECU Part No. Question

[Steve Eiche]

The early Immobilizers were pretty crude.  I knew that they were used in RS2, but hadn't known (or cared I guess) that the Euro C4 S4/S6s got them.  Anyway, the immobilizer code is contained in the EPROMs.  That means if you replace the late code with early code, the immobilizer goes away.  An early ECU in an Immobilizer car will run fine.  An Immobilizer ECU in an early car will not run, and will throw a code of "ECU Locked".   I first found this when I tried a late RS2 ECU in an S4 a few years ago. 

NO North American C4 S cars got the Immobilizers, so no worries there.

-- 
Steve Eiche
Shade Tree Software, LLC
http://www.shadetreesoftware.com   http://www.prodiag-hd.com
seiche at shadetreesoftware.com
800.419.6896

Dave Forgie wrote:

S-heads:

I was under the impression that the ECU in all our North American S4s and 
S6s was the same and had the same part number: 4A0 907 551 AA.

A fellow on the S2 forum from Lithuania ("kwlw") has suggested that the 
later S6s were equipped with a factory immobilizer, which makes ECU swap
 to S4 not possible without some cheating (and soldering). However, he is
 saying that an S6 can run with an S4 ECU.  I know I have tried Sean D's
 Dahlback-chipped 97 S6 ECU in my 93 S4 but we didn't try my 93 ECU in
 his car.

"kwlw" further suggests that the ECU part numbers are as follows:

S4: AAN Bosch 0261200465 VW Teile Nummer: 4A0 907 551 AA
S4: AAN Bosch: 0261200465 VW Teile Nummer: 4A0 907 551 A
S6: AAN Bosch 0 261 204 379 VW Teile Nummer: 4A0 907 551 F
S6: AAN Bosch 0 261 203 005 / 006 VW Teile Nummer: 4A0 907 551 B (Automatik)
S6: AAN Bosch 0 261 203 601 / 602 VW Teile Nummer: 4A0 907 551 C
S6: AAN Bosch 0 261 203 603 VW Teile Nummer: 4A0 907 551 D (Automatik)

Any ECU experts (Steve E.?) care to comment?