High Pitch Buzz In Engine Bay Killing Battery Nightly - Have To Jump Everytime I Drive It Now!

#1
2003 GMC Envoy SLT with 226K miles.

Lately I've noticed a faint high pitch buzzing noise coming from the engine bay when the engine is off. I haven't been able to locate it but it seems to be killing my battery quickly. I've had someone state it could be some module not "going to sleep" when the truck is off.

In the meanwhile it seems that when I drive the Envoy everything works just fine. Then when I turn it off its very difficult to restart it. If I wait over an hour the battery is dead and I have to use a jump box to crank it. (It used to be an overnight thing but over the last few weeks its now to the point where the battery is dead within the hour) Once cranked it runs just fine until the next time. I've had the battery charged and they can't find anything wrong with the battery. The alternator seems to be running everything just fine - although the gauge is not sitting at 14 anymore - a couple of notches to the left of 14 now.

Could it be the alternator - even though when the engine is on it seems to run the truck okay? The battery - even though when its charged it seems to work fine? Or should I be looking into a stuck module? Or something else all together?

Thanks to any and all replies!
 

The_Roadie

Founding Member
Administrator
#2
Welcome! COuld be lots of things, but having a noise associated with the problem is unique. But it makes it easier to troubleshoot - just start pulling fuses until the noise ceases. Then come back and tell us what one did the job. Then we can speculate a lot more accurately.

Read up a bit more on "parasitic draw". Tracking down stray module currents can be difficult if they take 5 days to drain a battery. Draining one in an hour or two implies it's about a 10Amp draw, and that should be trivial for anybody with a meter and some electrical experience.

That said - my initial guess, if you've never changed it, is the ignition switch can be failing in a way that leaves circuits energized that should be off when you remove the key. Pull underhood fuses #34 and #36 and see if the noise goes away.

It could also be your HVAC blower motor, assuming you're not getting the location of the noise accurately, and it's really behind the glove box and not inthe engine compartment.
 

kickass audio

Well-Known Member
#3
I have a high pitch buzz in my engine and have had that since day 1. It is coming from the PCM and it doesn't concern me as it doesn't kill the truck or draw any power more than like 12mA of current when off.

I would first try and see what voltage the battery reads at when you turn off the engine and see how fast the voltage falls down once it is shut down. My dad's truck had a bad battery that would die after a day of sitting and when I charged it up, it would charge to 14.2 like normal but once I took it off the charger it dropped down to 12.3 within 20 seconds which is way too low and too fast for a battery discharge rate. I tested the current draw when it was off and on and it was normal. I pulled his battery and it still dropped the voltage fast so it was a dead battery. Now before I say to pull the battery, be aware of pulling that will make you want to clean your throttle body and you may get a problem with your HVAC actuators if they are broken but if they are not, then you should have no problems. I'm willing to bet your battery is just kicking the bucket.
 
#4
This may sound crazy, but I think it may be the alternator. If you want to try it, disconnect the. Ground from the battery and then disconnect the large red wire from the alternator and wrap a piece of tape around it. Then hook the battery back up and see if you still hear the noise.
 

dfc739

Well-Known Member
#5
I had an almost identical problem with buzzing and killing a battery within hours. The relay for the secondary AIR pump had failed in the on position. Pull the hose off the valve on the side of the head and see if it's pumping. The relay is under the vehicle next to the AIR pump... it's a poor location choice IMHO.
 

gmcman

Well-Known Member
#6
BlazingTrails said:
This may sound crazy, but I think it may be the alternator. If you want to try it, disconnect the. Ground from the battery and then disconnect the large red wire from the alternator and wrap a piece of tape around it. Then hook the battery back up and see if you still hear the noise.
I was thinking that also, I would pull the signal wire from the alternator and see if the noise goes away? I agree it could be the ignition switch, if it does go away with the signal harness removed you could save your battery until you get it fixed.
 

Wooluf1952

Well-Known Member
#7
dfc739 said:
I had an almost identical problem with buzzing and killing a battery within hours. The relay for the secondary AIR pump had failed in the on position. Pull the hose off the valve on the side of the head and see if it's pumping. The relay is under the vehicle next to the AIR pump... it's a poor location choice IMHO.
The 2003 doesn't have the secondary air pump. At least mine doesn't.
 

Mounce

Well-Known Member
#8
Have you tried pinpointing the noise? I see that you said that you couldn't locate it but I feel like you could at least listen from different angles and figure out the general area of where it's at. Maybe open up the fuse box and feel each of the relays, I hadn't even thought of a relay going bad in your case until dfc mentioned it but anything is a possibility. Wooluf is correct though, 2003 doesn't have the AIR pump but it could still be some other random relay.
 
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startacus

New Member
#9
I really appreciate everyones comments! After checking all of this I was able to figure out the following: I did not have the secondary air pump. Pulling fuses 34 & 36 did not decrease the noise for me. However shortly afterwards the noise did cease because the battery died. So I took the battery out of my Safari, an Autocraft 650 and installed in into my Envoy while I took the Envoy battery, a DieHard 650, to Advance to have it recharged. I didn't have much faith in the Safari battery because the AutoCraft battery is 3 years old while my DieHard is less than 6 months old - AND that Sears had recently said it was good when all of this started. Anyways for the last 3 days since the AutoCraft battery has been in the Envoy I have not heard the noise at all! By now my Diehard battery would've been dead as a doornail. This morning after sitting all night for night 3 the truck started like a brand new battery was still installed. And there is absolutely no buzzing whatsoever. I didn't believe it was the DieHard battery because it is only 6 months old, AND that Sears said it was good. Advance said the DieHard battery was only holding 430 cca but I attributed it to the battery not having enough charge. Now I am convinced it is indeed the DieHard battery causing me all of this grief!!! So thanks for all of your thoughts! Hopefully Sears or Kmart or someone who sells them replaces this battery because theres no way I can rely on it anymore.
 

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