[Gmecm] Missing cam position signal in 1228253 ECM

[Scott Pearson]

Code 41 is often caused by a bad ignition module or the cam sensor magnet 
falling off the cam gear.

Your car probably has the Magnavox module (all three coils in one assembly). 
A good swap for these would be to grab the module and coils off a newer car 
with the Delco module. It's a plug and play swap.

Scott

----- Original Message ----- 
From: "kevin spears" <vega215v8 at yahoo.com>
To: <gmecm at diy-efi.org>
Sent: Wednesday, May 11, 2005 8:01 PM
Subject: [Gmecm] Missing cam position signal in 1228253 ECM


>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!
>
>
>
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