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Discussion Starter · #1 · (Edited)
I started driving my wife's 2008 Cobalt LT to work so we could save miles on our newer car. It sat for about the last 2 years since she was working from home. It is at 120k miles. Today after I picked up lunch it wouldn't start, no attempts at cranking the car. Dash lights up, radio is fine. This happened once before to me after work... I removed the key, waited a few seconds and then it was fine. Happened once and then no issues for over a week since then. She tells me this had happened to her every so often and she did the same, just took the key out waited a few seconds and then was fine.

So I go to Advanced Auto in the shopping plaza and the guy brings out his tester. We see the battery is pretty old, a little low on charge but still had almost 400 cca/590 cca which is enough to at least try to turn the starter. The ground terminal is pretty corroded too and the trunk had some water in the well. We try with a jump pack and it doesn't change, still no attempts to crank. I started doing some research and find the BCM issues with this car and how it controls the starter. I'm betting this is the same problem for me.

It did have some CEL, a few for the rear o2 sensor circuit voltage low/stuck lean, and then P2176 for Throttle Actuator A Control System Idle Position Not Learned

I'm wondering the best way to go about this and what is stopping it from cranking.
I pulled the 50A fuse in the trunk and the fuse ends and socket had some light white corrosion. I couldn't see a crack but I've had other cars where there was a hairline one. I cleaned the fuse with a stainless scrubby and it sparked when I put it back in the socket. I didn't have anything to clean the fuse holder though.

Should I just unhook all the connectors on the BCM, clean and grease them and reseat on module?
What are the chances of the fuse box being the issue? Since broken/cracked/corroded boards seem to be common culprit also. I just can't believe it'd be the fuse box after running just 2 minutes prior to picking up the lunch order.

The car is in a parking lot about half an hour from me right now, so I'd like to avoid having to tow it home if I can fix it.
Or at least "jump start" it somehow bypassing the starter controls and drive it back to work on in my garage.
I have tools and multimeter I can bring with me. I'm used to working on cars just haven't done much work on hers so no idea where some of this stuff is under the hood and honestly really hate electrical issues like this.

Can I jump the BCM/Starter Relay and just force the starter somehow?

Any help is greatly appreciated.

I just wanted to add I haven't seen other random electrical issues. Her gauges have been accurate, radio has been fine, turn signals, A/C etc, have all seemed to work fine the last few weeks I've driven it.
The security light looks like it is on on the dash. She doesn't have any power anything I don't think the key has a transponder in it.
 

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We had a non start issue on our '08. Everything else worked fine. We had a dead cell in the battery and the security light stayed on- no start- until I charged the battery. After charging we found the dead cell and a new battery fixed it for good. The computer needs a solid 12 volts so go ahead and clean all the battery connections. A little baking soda in soapy water does wonders to remove corrosion. A small paint brush or old toothbrush get into tiny crevices. Clean your terminals, charge the battery and see if that helps. Once the electrics are solid then see if the ignition switch is bad. Track down the ignition relay on the fuse/relay board and rig a jumper. When it happens, jump it, if it works then the ignition switch or relay is suspect.
 

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Discussion Starter · #3 ·
So I bought a new fuse because I saw fuzzy corrosion up both leads inside, cleaned the inline holder with baking soda, water and a toothbrush and some stuff dissolved. I pulled one of the crank relays in the fuse box on the right side I saw in a video for this issue and it had a little bit of corrosion on the bottom right leg, so cleaned that also along with the positive post. I didn't check the ignition switch relay though. I let the battery charge over night at home and also wire brushed the ground cable best I could. Reinstalled it all and it still won't crank. The security light stayed on for only a few seconds so it shouldn't be in theft deterrent mode.

I have a new ground cable showing up Saturday, and the only other thing I saw to try was reseat and dielectric grease the BCM connections and check the fuses there. I kind of feel dumb forgetting that today, but was frustrated that stuff didn't work and it was very hot and humid working in the parking lot! New ground cable shows up Saturday anyways so I'll check the fuses when I do that. I don't want to spend time out there with a multimeter, so if that doesn't work I'll tow it home and this thread will continue!

Really hoping that it is not a BCM or fuse box replacement but kind of looks like it right now. Thanks for the help and direction.
 

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I agree it is too damn hot to be fudging with stuff like this. But the multimeter is your friend. Do you have access to a spare battery and jumper cables? You can take a jumper and rig it to your battery cable at the starter. Put the ignition in "RUN" and jump start the starter. You may get lucky and it will start so you can get it home.
 
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