Re: Engine light on getting code 12

[Shannen Durphey <shannen@grolen.com>]

Sounds fine to me.  Code 12 with a&b jumpered is "no distributor
reference pulses", a condition you should definitely have if the
engine is not running.  Code 12 is sort of used as a sanity check for
the ecm.
Check other GM cars, you will find the same thing.

You haven't mentioned whether or not the engine starts, which would be
a key issue.  No pun intended. : )  No start with code 12 indicates a
need to make sure the dizzy is sending out pulses to the ecm.

I'm surprised that you don't have a service manual for that truck.  It
should have a description of the code, and a trouble tree for checking
it.

However, if want some personal attention, you can send your Sy to me,
a professional mechanic, and I'll volunteer to flog it-- I mean test
it and make sure everything is ok.
Shannen 


Keith wrote:
> 
> 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
> http://www.syty.net
> Direct Forum link -->>>
> http://www.syty.net/cgi-bin/fast-cgi/Ultimate.cgi?action=intro
> http://www.geocities.com/keith455
> http://home.tampabay.rr.com/keith455
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