[Diy_efi] ECM question

[Shannen Durphey]

billmiranda at netscape.net wrote:

> 
> I believe (wihout having it here in front of me) that I have the 1227165 ECU.
> 
> The 1991 corvette switched BACK to this ECM in 1991 but I am told that it's a MAP system... although... if it's the same ECM, can I NOT take my PROM from the 1989 IROC and stick it in the 1991 ECM?

1990+ Vette uses 1227727.  There was no "switching back."  There was a
new code version for 1989 Vettes w/1227165, but 1990 saw a new MAP
system with a new # ecm.  In 1992, the entire tuned port was dropped,
along with the 1227727.

> 
> This is my reasoning for this:
> 
> I have a 1991 Landcruiser with a 1989 IROC-Z 5.7 TPI engine (mildly modded out).
> 
> If for any reason (emissions?) they connect up to the ECM, they'll read a 1989 engine.  There's a company that can take my ecm, and program it to read as a '91 but I want to see if I can do this myself.  When plugging into the ECM,.. is the year read from the ECM, or the PROM?
The year is not "read" from these ecm's.  If there is any year checking
happening in the scan tool, it's based on a 4 letter "scan id" that's
available in the data stream.  The scan id would then be cross checked
against a database of factory released cal id's.  There is no other way
to verify which year calibration you have using scantool data.  Changing
the scan id is a minor issue, and myself and several othere here could
look up the scan id for a particular year car.


> 
> That ultimately is my question.
> 
Do you now have new questions?
Shannen

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