Low voltage issue

Tracy Wafer · July 15, 2021

I have a2014 GMC SIERRA 1500 5.3. I've had the battery, and the alternator replaced but I get this message periodically while driving as well as being idle. Any suggestions on what to do?

Jason Mitchell · June 29, 2022

I Have a Silverado 3500HD with the 6.0L Gas engine. I have a low voltage situation that I don't believe to be "normal". The dash gauge shows normal 13.8V upon startup, then a few minutes it drops to about 10V. The needle settles just above the lower limit for "normal". I know that the user manual and manufacturer specifications describe this as a normal condition, and the charging system will lower the voltage to extend the battery voltage.

Here's the rub. A couple weeks ago, I took the truck on a 5 hour road trip. I noticed the needle drop during this trip. I left the vehicle and did what I had needed to do. When I returned, the truck started normally and operated well for the trip home. I stopped for gas just before parking the truck for the night. After filling, the battery didn't have sufficient charge to start the vehicle. I had the battery and alternator tested separate by removing each component and taking to a test facility. Both were fine on the bench.

Why did I lose charge on the trip? Why do I never see the voltage gauge return closer to 14 volts? Anyone have experience with a similar condition?

swathdiver · June 30, 2022

The alternator will reduce output if it detects that the battery cannot take the charge. It's literally a smart charger that determines the health of the battery.

How old is the battery? I have had this happen and the battery was plumb wore out. If you have an advanced scan tool, in the BCM module, you can see the condition of the battery as the computer sees it, start up state of charge, previous start up state of charge, calculated temperature, etc.

Jason Mitchell · June 30, 2022

I did physically remove the battery and take it to be tested. I charged it before taking it there because I wanted them to do the load test while full. After the surface charge wore off, it held 12.6 volts and the test resulted at 1100 cranking amps.

That being said, it is the factory 2017 battery.

swathdiver · June 30, 2022

7 hours ago, Jason Mitchell said:

I did physically remove the battery and take it to be tested. I charged it before taking it there because I wanted them to do the load test while full. After the surface charge wore off, it held 12.6 volts and the test resulted at 1100 cranking amps.

That being said, it is the factory 2017 battery.

I don't think that's enough volts, If the ambient temp was 75 degrees, 12.6 volts is 75% state of charge. The shop manual for my truck (GMT900) says that when the state of charge drops below 64%, it's time to replace the battery. That being said, your battery is 5 years old or so and down here in Florida, that's old.

Check your local dealers for battery coupons, they may even install it/them for free.

diyer2 · June 30, 2022

Maybe I'm thinking wrong but with a 5 year old battery the first thing I would have done when that message popped up is put in a new battery. Going to have to buy one anyway, someday.