Engine light on getting code 12

[Keith <kgil1@tampabay.rr.com>]

This is on a 91 Syclone ECM 1227749 
I just replaced the engine in my truck and now when I turn the key to
 the "on" position the check engine light comes on. I short out the A &
B
on the ALDL and get a code 12. I've checked the "M" on the ALDL and it
 is not shorted and has 4.8V going to it. I tried a good memcal and new
 ECM and i still get the same code 12.
 Does anyone have any suggestions on what to do now?
 Is there a wire that i could have disturbed while replacing the engine?
 Thanks.

-- 
Keith Gill F.A.S.T.
Riverview, FL
'91 GMC Syclone #2173
'75 Oldsmobile Hurst/Olds
'92 Nissan Sentra SE-R
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