I have pulled the 46 relay and guess what...dead battery. I know I've shut it down in reverse (Tiered of the dealership asking that question) this is the 4th time first with the 46 relay out. FRUSTRATED! GM has to know about this and nothing is happening...no bullitens or nothing? what to do?

 

Have you had the battery itself replaced? Relay 46 is not the only cause of dead batteries and I know several people have had bad Delco batteries. Other factors like installed aftermarket electronics can cause dead batteries too. That doesn't mean that relay 46 isn't one of the causes for dead batteries.

Mike

 

I have had the battery change & no after market parts...maybe the 46 relay has been a cause in some vehicles...just not mine. Could it be something in my garage be causing somthing to turn on in the vehicle? (Garage door frequncy, my other vehicle computers?) probably grasping at straws but it always an adventure when I approach my car to get in...

 

GM appears to know something, but this LINK is all their saying so far...

 

I've seen that one. I think this is GM grabbing at straws since most people who have had DBS don't have LoJack or anything similar installed. Also, having something like that installed wouldn't explain why the battery only turns up dead once out of every 30 attempts. If a "security device" was preventing the BCM from shutting down, you should have the problem every time you turn the car off not just once in a while.

Mike

 

I would have to agree that a security device keeping the BCM awake would not be the only answer, however, I'm beginning to believe that it IS an issue with the BCM (or other control unit) not going t sleep, or perhaps waking up too often.

About 2 weeks ago there was a thread (EDIT: Oops, this was the thread! :o) discussing the amount of current relay #46 was capable of drawing and whether it was enough to kill the battery in some period of time. I decided to hook my DVM to relay 46's coil hot side to see what kind of voltage was there. What I found (at first) was 5 volts on the hot side and, of coarse, nothing on the low side. The BCM appears to ground the low side when (if) it wants that relay to come on. I probed a couple of other relays and found a couple more with 5 volts on the coil's hot side. This was strange since you would expect 12 volts. In fact, most relays had 12 volts at their coils. I figured that the few relays that had 5 volts (including #46) were being supplied voltage by the BCM instead of the main 12 volt buss.

To see if this was the case, I waited for the BCM to go to sleep by watching when the engine compartment light went out (auto shut-off). It did, and the 5 volts I was reading at the relays dropped top zero. Then I woke the BCM again by lowereing the hood and raising it again to get the engine compartment light to go on. This time I got 10 volts on the relays instead of 5 volts. I did this a couple of more times trying different things to wak up the BCM (open the glove box, turn on the map light). Each time I got 10 volts. Why I got 5 volts the first time is unknown.

The point of this whole thing is that it appears as if *anything* wakes up the BCM, a lot of things happen, including the power-up of the underhood relay box, the Nav's DVD spins, and who knows what else...

Here's a what-if: I read that the tire pressure sensors in the wheels *each* transmit every 15 minutes when the car is at rest. If each time a wheel transmits the BCM wakes up, and the wheels dont all transmit simultainiously, does the BCM wake up (up to) 16 times an hour?

I'd be willing to bet that GM knows precisely what's going on but the fix will cost them too much $$ for now so they're staying silent.

 

with the last statement...it's unfortunate...

 

Let's keep this all in a proper perspective. Most C6's have not had battery failures of any kind. This is probably the most common of all the complaints, but it still only affects a small minority of vehicles. Figuring out why some suffer from this and others don't is the real mystery. If the #46 relay is, in fact, one of the causes, then why doesn't it malfunction on all cars?

My car is subjected to the worst storage conditions during the winter months. It's kept in an unheated garage and ambient temperature can reach 35 below zero. We can stay below zero for many days at a time. When the temperature gets over zero, I usually start the car every few days and let it run for at least 45 minutes. It has always started the first time and cranked strongly. If the temperatures get above 10 and the roads are dry, it goes out for a drive. I have kept the original Delco battery and, as yet, have found no reason to change it.

I have the 1SB, no NAV, no OnStar, no XM, manual tranny. Homelink is used for a single garage door opener only. I have not pulled relay #46.

I hope I didn't just jinx myself. Watch...tomorrow my car will be dead.

 

my guess is that this is a bigger deal than even discussed on this forum. This is my second C6 and both cars have had the identical problem, could that be coincidence? That's why my guess is that it is something inside my garage or outside the car? I don't know but wow it's tough to swallow. Still love the car & enjoy every second driving it! That's why I tried a second one...