2005 Chevy Cobalt, Demonic Possession - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 8 (permalink) Old 03-16-2016, 02:34 PM Thread Starter
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2005 Chevy Cobalt, Demonic Possession

I have a 2005 Chevy Cobalt, 86k miles, and i will try to explain the best I can of what is wrong.

1. Left headlight sometimes works.
2. Left and Right turn signals/hazards flash randomly at varying speeds And sometimes not both at same time.
3. Power Steering indicator flash's on/off
4. Power Steering goes out, with and without indicator saying so.
5. Car seems to have a transmission issue, this one is hard to explain. I start moving the car and it drops RPM's or switches to a low gear, it struggles to get going until it switch's to 2nd gear, at that point its a rough transition to the next gear. It does so again going into 3rd. Have not taken the car on any main streets so dont know how it is above that.
Then, as I come to a stop, 3rd to 2nd is fine, 2nd to 1st.. well now the car wants to accelerate on its own. I have to push in on breaks much harder to get the car to come to a stop. As the car comes to the stop it then switch's back to the low RPM or low gear, what ever is going on there and the cycle begins again.
6. Radio Lock out.
7. Power reduced/Engine disabled, some times the car just dies on me while driving or just sitting.
8. After the engine decides to die on me the Security system acts up and the only way to get the car moving again is unplugging and re-plugging the ECM. Not always a fix, and sometimes not necessary.
9. Engine light sometimes on when this is going on. Even with the engine light on no reader has been able to even see that it is connected.
10. MPH gauge fluctuates by about 30 MPH, or just strait doesnt work.
11. RPM's fluctuates.
12. Remote access no longer works
13. Sometimes the AC thinks it is a heater.
14. Clock is reset when I turn on the car.

I think that sums up most everything. with the exception of the clock resetting, everything else had started happening little by little but now unsafe to drive in a months time.

Things I have tried.. I am not a car guy so I dont know what I may have missed.
1. Checked fuses both under hood and in the panel on passenger side at the BCM
2. Replaced the ECM
3. Read to clean a grounding point, attempted how ever it doesn't look like any corrosion is on it, not sure if there is a spray i should buy to really get in there and if i need to take the grounds off the bolt to clean it.
4. checked the battery. all is well, even looks brand new.
5. Prayed.
6. bought lotto ticket. Didn't fix it.

I feel it could be a bad BCM, but after the $900 for a ECM, and knowing the car has a PCM, BCM, TCM, and ECM, guessing that each of these cost about the same and all must be flashed I would like to know if I might of missed something.
If It is the BCM, where can I buy one new? Does New one need flashed at dealership? Do I disconnect battery before installing BCM?

well, Thanks for your time. hope I can get this fixed cheap soon. Or I have to buy a new car and I didn't want to have to at only 86k miles.
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post #2 of 8 (permalink) Old 03-16-2016, 04:15 PM
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Too bad you bought a PCM. You are definitely having bad connection issues. Try this but only one at a time. There are 2 blue gray connectors on the BCM. remove one and reconnect several times to clean the connectors a bit. If this cures your problem then give it a good cleaning. If it doesn't do the same to the upright one. Then come back and we'll discuss a bit more.

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post #3 of 8 (permalink) Old 03-16-2016, 04:38 PM Thread Starter
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next issue

Ok, so after posting my list of problems, I grabbed a wire brush and went to clean the grounding. went to start car and nothing, key stuck in ignition, cant move out of park. guessing dead battery. Looking for someone around that can jump start my car to make sure its not the ignition issue thats on recall.

I am guessing a bad battery could cause all the other problems too, if the computers are not getting the juice they need it would cause all kinds of stuff to happen. If bad battery is the fix I would be happy, but also feel bad cause I thought it was good.
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post #4 of 8 (permalink) Old 03-16-2016, 05:43 PM
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Could also just be the battery terminals being dirty.

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post #5 of 8 (permalink) Old 03-19-2016, 03:25 PM
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2005 Cobalt - Demonic Possession, Part II, Demon Rises

I, too, have the 2005 Cobalt demonic possession. While driving, all of these things happen at once and randomly:

Door locks locking up/down
Power steering light replaces odometer reading, sometimes just dashes ----
Speedometer goes to zero, jumps up and down sometimes
Tach jumps up and down
Dinging - crazy dinging
Gears slip (automatic transmission)
Can hear the RPMs go up and down
Air bag warning light, on and off (I am terrified!)
TC light, mostly constant
Bogs down, like it will die
Interior/exterior lights fluctuate

It is the most FRIGHTENING experience! Cannot drive this UNSAFE car. I contacted GM, got a case number. (There's no recall for this, though hundreds of people have this problem. Basically, they don't care.)

The 2005 Cobalt LS sedan (no frills) belongs to my daughter. I don't own a car. She works part-time and is in her senior year of college. We do not have $$ to go to the dealership to get ripped off. I am a computer geek, so I pulled the BCM and took it apart myself. The board looked good. I have checked all fuses to be good. I have cleaned/sprayed and greased the connectors to the BCM, ECM, TCM.

I am not a car mechanic, I'm a mom. But, I am doing everything possible to help my daughter. I have been reading all sorts of fixes (and non-fixes) for about 3 days now.

Coby7, I am starting to try checking all of the ground wires. I am not sure where all of them are, but I do know some. I have a question about this wire that I found below the oil stick. It goes to a black plug. Can you tell me if this pitiful-looking wire might have something to do with the problem? It looks like it has been modified before because it has nasty tape on it. Though it looks wet/oily, it is dry.

THANK YOU,
Amanda's Mom
(happy to help anyone with computer problems)

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post #6 of 8 (permalink) Old 03-19-2016, 05:04 PM
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Try adding a temporary ground between engine and chassis to see if it helps. Then you will be able to narrow it down to the engine ground.

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Drives 2016 Sunset Orange Trax LT1 1.4L Turbo auto 3GNCJPSB8GL142716

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post #7 of 8 (permalink) Old 03-21-2016, 09:05 AM
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2005 Cobalt - Demonic Possession, Part II, Demon Rises

Thanks Coby7. Tried that first, but nothing changed. Did the battery, battery cables, and alternator tests. Added a ground to the TCM. Driver's side door master lock had stopped working months ago, so pulled it out and unplugged it. Going to start checking for a short, one fuse at a time, while using multimeter to check for a drop. Thanks for your reply.
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post #8 of 8 (permalink) Old 03-21-2016, 09:14 AM
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There is a tie point for grounds under the driver's seat that sometimes corrodes and falls apart if you bring road salt in with your boots.

Every minute spent angry is a happy minute lost for ever and ever!!!
Drives 2016 Cocoa Buick Encore 1.4L Turbo auto KL4CJDSB2GB652675
Drives 2016 Sunset Orange Trax LT1 1.4L Turbo auto 3GNCJPSB8GL142716

Never drive faster than your guardian angel can fly
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