I want to discuss a problem I have and have seen other people with the HHR also have had from various Google searches.
Every now and then, at random, the battery goes dead over night. It could be hot or cold temperatures.
Checking with a volt meter does show voltage is low.
Checking charging system always finds it good.
Load checking the battery when fully charged also shows no problem.
Also my battery is only 6 months old. It was replaced under warranty for this battery drain problem with the thought the battery was defective.
I came across (by Google search) a person on this forum back in 2009 that had this issue. It was determined by a dealer that the BCM was bad and it was replaced and programmed.
I found an article that show problems with BCM's and it says parasitic drain.
https://moduleexperts.com/5-common-s...ol-module-bcm/

What are your views on this?

 

They list CEL as symptom #3. I guess they want everybody to replace the BCM if the CEL lights up.
More likely the action of replacing the BCM jiggles a loose wire and fixes the problem.
There are is a number of OBD2 tests that run while the engine is off, some run continuously under certain circumstances.
There is a case where a diode in the alternator is bad, turning the alternator into a motor when the engine is off but charges normally.

Blaming "bad computers" for everything is just lazy and expensive.

 

Being I don't have any high diagnostic tools this means nothing.
No check engine light also, has never lit up.

Don look thru the archives of this and see if you can find what I did.

I will say the Bluetooth at times work and other times it doesn't paired to my phone, which is related to the BCM.

I also had times when the car wouldn't start and I reset the BCM by pulling the 50 amp maxi fuse by the battery and reinstalling it.

Curious, how or if the BCM, can drain a good known battery over night.

 

I am going to say the BCM doesn't do it by itself, too. If there is an "iffy" ground somewhere, it might "see" voltage is too low. Something like that. I am a Chassis guy, but this just sounds like more research is needed.

Same goes for the ECM. And if it is a bad ground or loose pin, it will come back... No tech I know wants that.

 

What does the BCM have to do with BT? BT is part of the OnStar module. BT pairing probs are most often related to the phone, in my experience. The ONLY part the BCM plays is relaying the signals from the steering wheel buttons and the digital sound to the radio HU. The antenna on the phone is a tiny chip buried on the circuit board inside the phone; the antenna on the VCIM is on a chip buried inside the OnStar module; just holding the phone in a particular way could interfere with the signal or being near a garage door opener or any other consumer electronics wireless device.

Under some circumstances OnStar will attempt to "call home" and continue attempting if the antenna has been disconnected.

Under some circumstances the EVAP and other testing can get stuck in a loop.

DVOM is a "high diagnostic tool"? You can get one at Harbor Freight for under $5.

Go right ahead and replace the BCM, since the internet seems to say they are always at fault.

My point of mentioning the article and CEL was the article seems to say that ALL CEL are a fault in the BCM, not a fault sensed by a sensor then relayed to the BCM. The messenger is the problem. I guarantee that 90% of the people that read that page believe that is what is meant. It says "if there is a CEL replace the BCM".

 

Don
This is a discussion.
Not diagnosing.
It is a random problem that others have had and it's the same old story.
Oh your battery is bad, your grounds aren't clean, and so on.
Yes I brought up Blue Tooth (BT) as maybe a factor into the equation but I'm wrong with that.
So can it be possible that the BCM can, in some way, drain the battery low enough to not start the car ?
Knowing if the voltage is below minimum values the car won't start to begin with.

 

Sure, it is "possible". If I was throwing parts at the problem a BCM would probably be about #20 down the list.

BTW, only emissions related faults cause a CEL; there are lots of body codes that don't show up. Bxxxx and Uxxxx and Cxxxx codes don't necessarily trigger a CEL.

 

I will chime in with loose battery terminals, loose ground wires, a sticking relay in either fuse box, possibly even the relays for the computers.
Don’t rule out electrical gremlins without testing equipment.
May I ask have you performed a full 30 minute battery lobotomy? To reset the computers, if no codes then , try it.

 

Blue
This a very random event I'm trying to discuss here.
This car is in perfect running condition with 60K on it now.
Phantom problem started maybe at 40K
No accidents
Never been underwater, ect.
And yes the battery has been disconnected for 30 minutes a few times in the cars life.

 

I'll post this again for people to read:

https://moduleexperts.com/5-common-s...ol-module-bcm/