[Gmecm] Missing cam position signal in 1228253 ECM

[kevin spears]

I hate to burden the list with such a (seemingly) mundane question, but here goes.  I just picked up an 88 Park Avenue with a 3800 SFI V6.  It has a 1228253 ECM running ANBH 2522 code.  It runs, but has a persistent fault code 41.  According to the shop manual, code 41 indicates the ECM cannot see the signal from the camshaft position switch.
 
I followed the troubleshooting chart, and am convinced the signal is getting to the ECM.  I put a scope on the signal wire and got a waveform trace that seems roughly like what I would expect to see.  It is a VERY dirty squarewave.  I took a picture of the trace on the scope if anyone is curious :)  As further proof, I tried starting the car w/o the cam switch connected, and it won't run at all.  It turns over and fires for approx 1 second, but then dies right out.  With the sensor connected it starts and runs.
 
Anyway, the shop manual says that if a signal is present at the ECM harness, then the ECM is bad and should be replaced.  Seems a bit odd to me, as past experience has shown me that the ECM is usually the last thing to fail!  Especially on a motor that runs fairly well like this one.
 
Does this ECM have a bad reputation for failures?  I suppose it wouldn't be difficult or costly for me to bring one home from a junkyard to compare results with, but if there's something else I've overlooked I might as well try it first!
 

		
---------------------------------
Do you Yahoo!?
 Yahoo! Small Business - Try our new resources site! 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.diy-efi.org/pipermail/gmecm/attachments/20050511/26a42feb/attachment.html