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Registered
2007 CTS 3.6 >131k miles
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701 Posts
BTW I don't know if GM calls it a PCM or an ECM. In my world they are the same thing!
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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322 Posts
Discussion Starter #24
Well, it wouldn't start this mrng. No CE lite. Did battery reconnect and it started, but the Trac Control lite was on. That makes it shift hard. Turned it off n back on and it went out and drove excellent. After sitting 7 hrs, it did it again. Did battery reconnect and it started with no lites and drove fine, all way home. Am still thinking ECM, but haven't had time yet to mess with it anymore. I've got a Snap-on Ethos Pro scanner. Its bi-dirrectional, but I haven't figured out how to do anything more than read and clear codes with it!
 

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Registered
2007 CTS 3.6 >131k miles
Joined
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701 Posts
That is really strange! Quite possibly the ECM but could also just be the connection. I would rule this out first (disconnect and blow out the connectors as I suggested above). I always consider ECM replacement as a last resort, given that it costs a lot more than the basic stuff! Hopefully you resolve it soon.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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322 Posts
Discussion Starter #26
Will do. I've got a can of electric cleaner. I'll take the plugs off both tcm and ecm and use a toothbrush and spray clean them. The other plug-ins there too. This weekend. Thanks Ryan. Right now I'm gonna research the tsbs for the p0100 and also the can bus locations for the e and tcms. I saw that used ecms are pretty cheap online. I also need to find out if and how to program one. With my scan tool, hopefully.
 

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Registered
2007 CTS 3.6 >131k miles
Joined
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701 Posts
I would not use a toothbrush! Lots of very thin gold pins that bend easily. Just spray the electrical cleaner and blow with air (I avoid any physical contact with the pins). It won't be gunked like other things under the hood, but may have a speck of dust or two causing issues. The outside of the connectors will likely be covered with dust and the locking lever will likely be stuck, but it will flip outward with gentle pressure and patience (I struggled the first time I did one of these, mostly because I was afraid I would break it).

Again, this is purely speculation but worth ruling out before replacing the unit.
 

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Registered
2005 Base CTS work at Pullen solenoids Glass Factory for 36 and a half years
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175 Posts
Hey TA Coupe, xactly what are you talking about? I dnt get it.
Sometimes when you clean your battery post and cable clamp you will remove move enough material that the clamp will not tighten down good anymore. I had this happen on my wife's Toyota. I would tighten it down as much as I could and it felt like it was tight because I couldn't move it anymore. But over time I guess from vibration it would come loose again and I tighten it again and it would happen again so to solve that problem originally I striped some wire and put it between the post and the clamp and that worked. One day at AutoZone I was looking at the battery cables and noticed a little box with two metal caps in it and wondered what it was. They are made to slip over to the battery post when you have this problem and it will make up for the material that has been removed from the post and cable so that you can then tighten it down enough and it will stay that way. You will have to be able to open up the clamp on the cable to get it to fit over it though. You can also just buy the new cable and hope that that will tighten up enough. You also have to have excellent grounding on cars that use computers. Hopefully this makes it a little clearer about what I was trying to say.

Roy
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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322 Posts
Discussion Starter #30
Thanks TA, I ddnt know about those. My CTS is side post. I found a better bolt that was threaded all the way to head. A lot of them aren't. That fixed mine.
 

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Registered
2007 CTS 3.6 >131k miles
Joined
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701 Posts
Thanks TA, I ddnt know about those. My CTS is side post. I found a better bolt that was threaded all the way to head. A lot of them aren't. That fixed mine.
Are you saying it was the battery connection that was causing the problems all along? It always makes me happy when I spend a lot of time exploring an issue but then it ends up being easy/cheap to fix!
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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322 Posts
Discussion Starter #32
No no! Earlier in this "problem", I discovered the bad bolt, loose cable n fixed it, but it still did the same thing the next day. This mrng it started right up, no lites, drove great, but last nite I did smtng different! I shut off the HVAC and the radio, before I shut down the ignition. Because, the day bfre, when I attempted to start it, I noticed the HVAC and radio both shut down when I turned the key, and I had to do the battery reconnect, to reset everything and get it started. I'm gonna clean those plug ins, this weekend.
 
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