Getting our 2014 GMC Acadia back from the shop today. Check engine light came on last week, throwing a P0300 code, random/multiple engine misfire detected. Got it to the shop and have been working on it since Monday. They replaced 2 of the 3 catalytic converters and the spark plugs. Running fine now but have a question.

On Wednesday, after replacing the front converter, they ran it for a bit and said it ran fine for a time. Then it died on them and wouldn't start and acted like the battery was dead. They checked the battery and it showed 4 volts (battery is fairly new).

When it died originally, we were getting error messages like service Stabilitrak and Traction Control on, Traction Control off.

That, combined with the battery issues concerns me that there may be an electrical issue as well. I know chasing electrical ghosts can be a nightmare so I wanted to check with the experts here if they have ever seen these combination of issues before.

I'm considering going ahead and getting a new battery, even though the current one is only probably 2 years old.

Thanks in advance.

On my previous Cadillac CTS-V (2011) I would get all kinds of strange warnings if the battery got below 11-ish volts. If it were me I would replace the battery, especially if it went to 4 volts. Often running a battery low will damage it.

I would go ahead and throw a new battery in it and see if that clears up the problem. If not, the vehicle may have a parasitic draw or ground problem.

I’d also try and rule out a bad Alternator as well. I think you can do it with a multimeter or take it to autozone and have them run the test.

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Originally posted by JohnV:
I’d also try and rule out a bad Alternator as well. I think you can do it with a multimeter or take it to autozone and have them run the test.

Good point. With the engine running, set your multimeter to DC volts and measure between the positive and negative battery terminals. Make sure all your accessories, headlights, etc are off. You should have between 13.8 and 15.2 volts at idle.

If the engine is off you should have a minimum of about 12.2 or 12.3 volts. Less than that and the battery is bad.

Ensure there isn't a grounding strap yanked off somewhere.

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Originally posted by Mars_Attacks:
Ensure there isn't a grounding strap yanked off somewhere.

Where would I find that?

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Originally posted by PowerSurge:

quote:

Originally posted by JohnV:
I’d also try and rule out a bad Alternator as well. I think you can do it with a multimeter or take it to autozone and have them run the test.

Good point. With the engine running, set your multimeter to DC volts and measure between the positive and negative battery terminals. Make sure all your accessories, headlights, etc are off. You should have between 13.8 and 15.2 volts at idle.

If the engine is off you should have a minimum of about 12.2 or 12.3 volts. Less than that and the battery is bad.

I'll check that when I get it home. I think I'm going to go ahead and grab a battery on the way home also and change that out. I can't figure out why it would read 4 volts, then be fine and no symptoms at all later. Maybe a bad cell, although wouldn't that show up?

I am not a mechanic but I am the fleet sergeant of my sheriff's office. I have seen bad batteries do some crazy things to vehicles.

Another battery related item - check the cable ends and terminals. If theres any buildup, use a battery terminal cleaner and follow up with the felt terminal rings and protectant spray on the posts.

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Originally posted by Erick85:


I'll check that when I get it home. I think I'm going to go ahead and grab a battery on the way home also and change that out. I can't figure out why it would read 4 volts, then be fine and no symptoms at all later. Maybe a bad cell, although wouldn't that show up?

Two years old is nearing replacement time for most automotive batteries. If it's been run down a time or two, then it's definitely time.

To test the battery, it needs to be charged first; fully charged outside the vehicle, then a specific gravity check done on each cell. What's most important isn't the specific gravity, but the consistency between cells. When you have 4 volts, you have an indication of multiple cell failures and a good chance your battery is shot...but it can't be tested until it's been charged overnight. Once it has been charged, it needs to be checked not just with a voltmeter, but a load tester to check capacity.

With a new battery in place, you'll need to do as another poster cited above; check for voltage as installed, and then voltage with the engine running; you should have approximately 2 volts more with the engine running than with the engine off. This is checking your charging system to ensure you have a higher voltage. To properly check the charging system, you'll need to load check that, too; most automotive stores will do that for you at no cost.

Spark plugs and cat converters going out at once? Unlikely, but it may be that the plugs were getting worn and needed changing. It sounds more like your mechanic isn't troubleshooting, but is taking a shotgun approach and throwing parts at your car in the hopes that something will fix it.

The fact that your mechanics ran the battery down to four volts and didn't catch that sooner or test it or check suggests that you might want to look at getting a different mechanic.

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Originally posted by sns3guppy:

Two years old is nearing replacement time for most automotive batteries.

Say what?

My wifes car had a battery that would show great at times and dead at others. It had an internal break that depending on how it was sitting would depend on if it worked or not.

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On Wednesday, after replacing the front converter, they ran it for a bit and said it ran fine for a time. Then it died on them and wouldn't start and acted like the battery was dead. They checked the battery and it showed 4 volts (battery is fairly new).

They shouldn't have let it leave their shop after that. If the battery goes dead while the car is running, something is very wrong with the battery, wiring, or charging system.

I hope you find a better mechanic.

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Originally posted by Some Shot:

quote:

On Wednesday, after replacing the front converter, they ran it for a bit and said it ran fine for a time. Then it died on them and wouldn't start and acted like the battery was dead. They checked the battery and it showed 4 volts (battery is fairly new).

They shouldn't have let it leave their shop after that. If the battery goes dead while the car is running, something is very wrong with the battery, wiring, or charging system.

I hope you find a better mechanic.

This was 2 days ago. It hasn’t left them.

Batteries in newer cars seem to be pretty spotty in terms of quality and longevity. It's not uncommon to see them die after 2-3 years anymore and is most likely the source of your "electrical" problems you believe you have.

In my experience whenever voltage drops below 9v the computer modules start going retarded and doing weird stuff. I would without any doubt replace the battery and re-start diagnostics.

I learned on day 1 of the job that you start with 12 volts in the battery and gas in the tank before looking at anything else on the vehicle.

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Originally posted by Balzé Halzé:

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Originally posted by sns3guppy:

Two years old is nearing replacement time for most automotive batteries.

Say what?

Two years old is nearing replacement time for most automotive batteries.

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Originally posted by sns3guppy:

quote:

Originally posted by Balzé Halzé:

quote:

Originally posted by sns3guppy:

Two years old is nearing replacement time for most automotive batteries.

Say what?

Two years old is nearing replacement time for most automotive batteries.

I am also surprised by this. I routinely get 5 or more years from car batteries. That's on five different vehicles ranging from 4 to 8 cylinders and two diesels.

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Originally posted by sns3guppy:

quote:

Originally posted by Balzé Halzé:

quote:

Originally posted by sns3guppy:

Two years old is nearing replacement time for most automotive batteries.

Say what?

Two years old is nearing replacement time for most automotive batteries.

What crap batteries are you buying?

Most new cars come with the cheapest battery one the company can buy. Two years or so is normal in my experience...if you are the originL buyer and it is now five years old, replace the battery