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2014 Malibu LTZ 2.5L
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Discussion Starter · #1 ·
2014 Malibu 2.5L LTZ

I have been having some ongoing problems. My battery seems to not be getting charged. I replaced the battery under the hood last summer (2020). A couple months ago i replaced the alternator. I was still having issues so took to Autozone to have it tested. They said the new alternator was over charging. However when i look at the battery voltage in the menu while driving i see 13.5v - 14.2 volts. Yesterday while driving i did see this drop to 12.8 while driving on the highway with the AC on. So it doesnt seem to be over charging but does seems like there is something else going on.

The auto stop doesnt work like it did before. It doesnt shutoff at stop lights as much. But when it does auto stop when it starts back up i will see a flash on the computer menu saying Service Charging System and the red battery light will come on and go right back off.

I scanned the codes and see these:

C0800
P0621

71171


Anyone have any ideas?
 

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I would take the autozone advise with a grain of salt, particularly with this vehicle. For example, you don't have an alternator in this vehicle, you have a 150v water-cooled generator. Plus, if their meter is not reading all the modules in this vehicle, you only have a partial picture of your event.

I had a similar problem with my Generator Control Module (GCM) and when I would have problems with it, naturally the charging system would code, plus I would have a slew of other seemingly unrelated codes like you are experiencing, everything from "battery saver" mode, elec. park brake, ABS, Aux. battery cooling fan shut off, etc. Essentially I felt like when the GCM was faulting and the charging system was impacted, this vehicle was proactively cutting power to other systems which in turn would cause them to code (and this is just a gut feeling based upon the fact that when the GCM was repaired, all other codes stopped). However, I did have codes directly related to the hybrid charging components once a proper meter was used to diagnose.

What meter are you using here and does it read ALL the modules in this vehicle?
 

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2.5 is not a hybrid motor, regular alternator. Battery in trunk need to be checked also.
 

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2014 Malibu LTZ 2.5L
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Discussion Starter · #5 ·
I did have the trunk battery check and they said it was ok. I will say its the original trunk battery. I didnt want to replace it on a hunch since its $100
 

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I would say have the battery in the trunk checked in a proper manner. I think that means isolating it and load testing it.

If the flash message is occuring just as the autostart is working, I'd guess the rear batter because that's the only time it is used--it supplies power to the car's ancillary devices so the starter can use the main battery for cranking the engine and that's only during the cranking process on auto restart.

Then the DBM (dual battery module) returns all circuits to the main battery. So a warning from the time period might indicate rear battery. I believe I found Oreillys (Checkers) has the right replacement battery for rear since I've been reading as others have had to replace theirs and I've noted where they found replacements.

There is a possibility of a problem in the DBM or some wiring. There are a couple of long videos troubleshooting the batteries, wiring, and DBM.

I also have a 2014 2.5 with original batteries front and back. it has 40K miles and has been garaged so batteries haven't seen extreme cold or extreme heat other than sitting on a few summer vacations at motels.

I assume you replaced the main battery with an AGM battery?

The reduction in voltage after a period of time where the quantity of power drawn from the battery has been replaced with the charging occurs normally and improves gas mileage by reducing the drag on the alternator. It's supplying only enough voltage to carry the load as the car is being driven at 12.6 or in your case showing 12.8 v. Both my Chevies do that (2015 Cruze).
 

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7 yr old batteries are always suspect, even if they ''test'' OK.
Lots of 1 and 2 yr. old battery failures, at 7 it's time for it to be replaced. Battery issues are one of the primary sources for vehicle complaints / issues today as our computers on tires heavily rely on a healthy battery.
 
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2016 Malibu 1LT 1.5T/6-speed 6T40
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7 yr old batteries are always suspect, even if they ''test'' OK.
Big time. Over the years I've read dozens of posts from users with an electrical issue and an older battery that "tests ok not the problem". Only after days or weeks of back and forth they replace and the problem goes away. I wish mfg would put battery replacement on the service list - something like 4 years or 80,000 miles. A battery shouldn't need to leave you stranded or stuff start choking before it gets replaced.
 

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2014 Malibu LTZ 2.5L
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Discussion Starter · #10 ·
Thanks guys. My guy replaced the alternator the other day while i was out of town and i got the car last night. He said he has driven it a few times to work and all seemed normal. The auto stop happened on my way home and no message. I came home and mad sure the battery was charged back to 100% with a charger. I will be keeping an eye on it the next few days.

I found the aux12 battery from Amazon for $95 which was the cheapest i found and its an AC Delco.
 

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Discussion Starter · #11 ·
Just a quick update. After the alternator had been replaced i cleared all codes.

Drove yesterday for a couple hours. I didnt seen any errors during the auto stop which is promising.

I rescanned the computer and the C0800 and P0621 codes are gone.

However i have a couple new codes that poped up i need to watch. I got the following 2 codes.

U0073 Status History Control Module Communicatioin Bus A

U0422 Status History Invalid Data Recived from Body Control Module
 

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I get random U codes all the time. If everything is performing fine just clear them. If U codes appear along with any P, B or C then start looking at those first.
 
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