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Hi,

This is an ongoing problem I"ve had for the last few years :roll: At first I thought it was from the cold when I had the vehicle maybe a year
and it got cold. I would put a heater from the house up on the hood with the hood open and after about an hour it would start. Well this went on
for maybe 2 years and then last year it progressed into a real problem. The dash lights went on and no crank, so I was ble to at some point finally
get it start went to an auto parts place got a battery and for the most part it didn't really cure the problem but I was able to get home.

Then I thought I'd learned that through all the lights in the dash board that maybe it was an ignition switch so I replaced that and it seemed to help but there was this intermitted problem yet with it not wanting to crank. After taking it to a auto place in town that I do some work for periodically they tore it apart they said and cleaned connections yada yada put it back together. I got there it did start got home and a day later we were back at it :( No crank, well I was as you can imagine starting to get more than a bit frustrated at this point because now my ventilation system was acting weird for a bit also and the air was on but I couldn't change the ventilation from out to in I think was what it was but no matter that all straightened out after I got frustrated and pulled the bottom panel off, I looked around couldn't figure anything out but it started!

I put the panel back on and it didn't start, so hey I thought I'd at least figured something out which I know was nothing but none the less I was getting to where I had to go, wires and panel hanging down on my legs making it hard to drive or not I was getting there, lol. Well now after about 6 months of good luck replacing some coils and being thrilled that this thing was even starting really well in the cold weather, well you guessed it my luck ran out and the thing stalled on me as I drove off from a job bid I had just been at. The heavy sinking feeling set in and I called my wife she got there I called a tow and outside my office window it sits :( I've tried a few different things, I found a pretty helpfull video on Youtube where I learned to jump and test the starter relay.

The starter did in fact engage but in between this I went to reference the video and just to see if there were any responses to my inquiries, none :( But none the less I did rewatch the video. I'm trying to run my business and work on this truck, lol, not a good combination as half of what I think I know goes out the door as I go out my door to try and work on this. So I am seeing that there was one thing I didn't test quite right, but here's the kicker on this, I was chatting with a friend of mine last night on this and he asked me if I had taken battery terminals off and cleaned the wires, well wires off :) I just kind of wiggled the ground wire on the battery and for the heck of it went in to try it and for the first time in like 3 weeks now it was cranking but not long enough to start and I was right back to square one.

Man I just don't know, I figured that this had to be it and then I start to think maybe a fluke? I took both wires off the side mount battery terminals and cleaned and tightened up with reasonable force with no relief in sight. I also by a recommendation of someone from another shop took the alarm out of the line and that did nothing either. Waiting for my wife to come home and I'm going to go out and test the ground terminal for the starter relay that I didn't test correctly just to see what results I get from that, maybe there is an answer there? It would seem something isn't grounding properly is about all at this point this novice can figure out. The video I was talking about is here http://www.youtube.com/watch?v=iMzdYCA0s2w If you've taken the time to read all of this, first I apologize for the lengthy to do but I felt that the history of this problem might offer some clue as to what is going on and then secondly I thank you for having this much patience :oops:

I'm just a small business owner who doesn't have a lot of cash to throw or I'd probably buy a new truck but besides the starting problem this thing runs awesome as I've taken the best care of it that I know how to. Anything you can offer up I will more than appreciate I promise :) Heck if you lived in my area I'd come to your house and clean your carpet free of charge if you could help me out :) I'm out in Hendersonville TN. If you have any relation out here and you can help me out consider a free job of carpet cleaning done!

Thanks in advance :)

Scott


   
 

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contributions: 307
Images: 4
OK. So if i am following all this correctly, the main problem is it won't crank when cold and it won't crank now?
But you also stated that it was running, and stalled out recently?
You had a non-factory alarm in it, but that has been removed now? Are you sure you got ALL the alarm components out iof the system? All reconnected with good connections? The reason i ask is many times people think they took the alarm out good enough- Meaning there are still some relays or a module hooked up, but the truck starts and runs so people think that was good enough.
Is this correct?


Last edited by TerryAuto on Fri Feb 01, 2013 6:38 pm, edited 1 time in total.

   
 
 

contributions: 6
Hello and thank you for your response,

As far as I know the entire alarm was out of the line and from what I've seen of other Trailblazers of that year in videos trying to figure this mess
out it looks to be a factory alarm. The alarm is connected inline meaning that clamps are secured to the wiring, not connecting one side of the circuit to the other. I have since put it all back in place as it would seem from what I could tell that it wasn't making any difference. There were two modules to this alarm as far as I could tell. The other questions, far as it starting when cold, that was in the beginning of this all, then it just started to become a problem off and on all the time no matter what the weather was. Yes it stalled out 2 weeks ago and has sat outside my window too many days and it's driving me crazy :( Yesterday when I wrote this after I wiggled a bit on the battery ground cable and went in it cranked for like probably 5 seconds and it went right back to a dead silence. I need to get it figured out asap, so if you have any ideas that would be great! Also I tested the ground from the relay yesterday and that is functioning properly as well. So at this point I am getting a plugin reader in hopes that I can maybe get some codes out of this thing's head to try and learn what is wrong.

Thanks


   
 
 
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contributions: 307
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OK. You need to step back a little and do some basics for the no crank.
Swap the crank relay with another one or just replace it.
If that does not help, when it is not cranking, use a test light to see if there is power on the purple wire at the starter. If there is, the starter is bad. If not, then work back towards the crank relay looking for a wiring problem. If you dont have a test light, get a long extension and bang on the starter when someone has the key turned to crank.


Last edited by TerryAuto on Fri Feb 01, 2013 6:38 pm, edited 1 time in total.

   
 
 

contributions: 6
Hi,

I replaced the relay as well as if you go back and read my original post you will note that I have done all the steps that are in the video.
Starter relay was jumped at the terminal starter engaged, meaning no troubled wiring. Also ran a diagnostic on it now and no problem codes
are coming up. I'm really running out of answers as to what this could be, my gut feeling is that there is a shorted wire somewhere under the dash or something. Doesn't make sense


   
 
 
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contributions: 307
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Well i did not watch the video. I know how the system works.
OK. Everything from the relay to the starter, and the starter, are good. So yes you have a problem before the relay. The PCM activates the relay after it sees the ignition is turned to crank. Since it used to have an alarm and your are sure all the wires are good, then you may have a bad PCM.
If you grounded the relay to activate it, you are basically doing what the PCM is suppose to do.
Is the ignition switch sending crank signal power to the PCM?


Last edited by TerryAuto on Fri Feb 01, 2013 6:38 pm, edited 1 time in total.

   
 
 

contributions: 6
Yes I tested all the terminals on the relay and with key on and turn to start there is a signal being sent for request's to the pcm.
The only thing I can't explain is that yesterday when I wiggled the terminal and the starter engaged, I don't know personally, not knowing
of course all there is to know about the brain aspect of this vehical is I would think if it were a bad pcm how after it was bad would it accomplish
the starting mechanism? If it were dead fried or that function quits working that should be it, but again I am no expert :)


   
 
 
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contributions: 307
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OK, so wiggle that battery ground again with someone holding the key in crank to see if you can duplicate it again. You could have a bad connection under the insulation, or moving that cable also moved a wire touching it down the cable somewhere. This system is very touchy. If not enough voltage, it will not crank. These trucks dont even do a slow crank very often when a battery is weak, they just wont crank at all.

If you can confirm ignition voltage into the PCM, check that the computer is grounding the wire for the relay RIGHT AT the PCM terminal? If not, the pcm is bad. If yes, that wire from PCM to relay is bad somwhere or the problem is internal to the fuse block under the hood.

All this needs to be checked while it is a no crank condition.
PCM is a computer and they will do strange intermittant things. Not always just straight forward- its bad and will never work again. They can come and go.
_______________

Be sure to check the Similar questions down this page for more help.


Last edited by TerryAuto on Sun Jan 27, 2013 11:25 pm, edited 2 times in total.

   
 
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