Buick ECM Trivia

[Ludis Langens <ludis@cruzers.com>]

I've discovered some interesting things about the ECMs used with the
Buick 3.8 and 3.0 V6's.

The 1226461 and 1226459 ECMs (1984-85) contain the exact same mask ROM
code.  The first is a batch fire ECM, the second is SFI (used only in
the GNs).  Needless to say, the ECM hardware is way different.  The
'6461 is mostly all on one board with just a little daughterboard
holding not much more than the EPROM.  The '6459 contains two full size
boards.  The EPROM holding the calibration data also contains some
program code.  It is different between these two ECMs.  Presumably, SFI
mode is software disabled in the '6461.

Similarly, the 1227153 and 1227148 ECMs (1986+) also contain the exact
same mask ROM code.  The first is batch fire (3.0 only), the second is SFI.

This explains why the first pair of ECMs both have a mask ID of 29/$1D,
and why the second pair both have 49/$31.  Much of the table layout
should be identical between the batch and SFI versions of each pair.

Note that there is a third ECM with the ID of 29/$1D.  This is the
1226948.  The mask ROM in this ECM is different though.  After a quick
look, the first half or more of the calibration data has the same layout
as the '6461 & '6459.  Toward the end it does differ slightly.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/


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