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08 Cobalt Won't Start. Please Help.

First I'd to start off by thanking everyone in advance for any help provided. My girlfriend owns a 2008 Cobalt and this morning, after driving fine for months, just simply would not start. The motor turns over fine but won't start. Before we get into that, a brief history of the car....a few months ago her automatic door locks went haywire and were open/closing non-stop. I did some research and found that most people point to the BCM for this problem. I just pulled the fuse for the auto locks and called it a day. The car has been running fine since. About 4/5 months later (today) she went outside and the car would not start. Ive been tinkering here and there and after a little research I found that this issue could be one of many problems including the BCM.

I disconnected the batteries and pulled the big red plug out, blew out any dust, slapped some Dielectric grease on it and plugged it back in.

After this, I jumped in to start it.....started up right away. I even drove it around the block and let it run for a few minutes. Ran fine.

I turned off the car, got out, and hung around for a bit.

I went to test it again. Car started...idled fine for 15 sec and just died. It is now back to not starting. The engine turns over but the car does not start.

Any Ideas???
 

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You might have corrode fuse tabs. Pull fuses pertaining to engine under the hood. Pulling and re-inserting will clean the tabs enough to get a good contact. But I have a funny feeling it might have to do with the fuel pump or fuel filter is pluged.
 

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Levee
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First I'd to start off by thanking everyone in advance for any help provided. My girlfriend owns a 2008 Cobalt and this morning, after driving fine for months, just simply would not start. The motor turns over fine but won't start. Before we get into that, a brief history of the car....a few months ago her automatic door locks went haywire and were open/closing non-stop. I did some research and found that most people point to the BCM for this problem. I just pulled the fuse for the auto locks and called it a day. The car has been running fine since. About 4/5 months later (today) she went outside and the car would not start. Ive been tinkering here and there and after a little research I found that this issue could be one of many problems including the BCM.

I disconnected the batteries and pulled the big red plug out, blew out any dust, slapped some Dielectric grease on it and plugged it back in.

After this, I jumped in to start it.....started up right away. I even drove it around the block and let it run for a few minutes. Ran fine.

I turned off the car, got out, and hung around for a bit.

I went to test it again. Car started...idled fine for 15 sec and just died. It is now back to not starting. The engine turns over but the car does not start.

Any Ideas???

First let me start by saying welcome and thanks for joining! Now to help you out a little bit. A little more diagnostic information can go a long way. In order for any engine to run it needs air, fuel and ignition. IF you pull out the spark plugs, look at them and see if they are wet and smell of fuel. If they are, you may need to replace the spark plugs as they may not be sparking. There are ways to test this and I'm positive someone here can tell ya (as I don't have a whole lot of time to explain it right now). If the plugs are fine, check your fuel system. I know it's vague, but I'm positive someone can help you until I can get back to my computer to help. If it hasn't been figured out by then, I'll be more than happy to go into further diagnostics on your car for you and this will all be stuff you can do willingly without a mechanic. :)
 

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Discussion Starter #4
Thanks for the responses! Ill be getting back at the car tomorrow morning so I'll be posting early with any new updates.
 

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So, really strange.....before I went to do anything to the car I tried starting it and it turned on right away! Even drove it around the block again and it drove as it would normally. I'm still going to do some basic diagnostic stuff and Ill go through some fuses. Will update soon.
 

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Pulling and re-inserting each fuse after 5 years is always good preventative maintenance. An other good perventative action is to remove all "TCM,ECM and BCM" connectors and re-inserting while inspecting for corrosion at the same time. Disconnect battery before doing this though. There is also a big "BCM" fuse in the trunk beside the battery.
 

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Discussion Starter #7
Alright so like I said earlier the car ran fine. I decided to pull the plugs anyway....they seem fine. The air filter is only like 2 months old. Any way, I left the car alone for a while and figured the lady and I take the Cobalt out for our errands. We got in to try and leave and again back to not starting. The car is not bogging or choking just deciding not to start. Im going to go back out in a few minutes to mess around again. Will let you guys know anything else I find.
 

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Might want to look at ground connections then. You pulled each fuses right? You pulled each connectors too right?
 

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Hey all.....sorry I get pretty busy throughout the work week and didnt get to mess with the car. @Coby7, yea I pulled each one.
 

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There are several ground connections, the main one is the 2 big ones on the front of the engine block where it meets with the transmission. There's one on the radiator support driver's side just above the headlight, one under the coolant reservoir, one on the driver's side strut tower. Maybe try cleaning the "CPS" connection.

I was reading your first post again, and your Cobalt seems to be displaying the symptoms of a faulty "Crank Position Sensor" except for the part where it died 15 seconds after starting. Usually if it starts and "CPS" is faulty it won't die until you shut it "off" and then won't restart. If you have a faulty CPS the ECM won't know how to set the firing order and car won't start. But if it's already running and loses CPS info it falls back on Cam position for spark. I believe this would set a code though. One of these quite possibly....

P0385 Crankshaft Position Sensor B Circuit Malfunction

P0386 Crankshaft Position Sensor B Circuit Range/Performance

P0387 Crankshaft Position Sensor B Circuit Low Input

P0388 Crankshaft Position Sensor B Circuit High Input

P0389 Crankshaft Position Sensor B Circuit Intermittent
 
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