At idle the voltage can drop.
And as 19963.4lsr5 said, best to measure voltage at the battery.
Have you done a load test on the battery?

Hot idle at 650rpm voltage stays at 14.1v putting down the window.


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Let me start by saying thank you all for all of the great information that you have shared. It has been truly helpful. However, I still suspect that the battery is on its way out. I'm still getting the P1130 and P1135 codes when the voltage drops, and only then. On top of that it started turning over longer before the engine starts, and now making a slight grinding noise while turning over. So, yes possibly the starter is also starting to go, but I need to make sure the power is sufficient before addressing the starter. I drive about 50k miles a year up and down the East Coast on marathon style trips that can sometimes be up to 2000 miles in less than 36 hours. So what batteries out the will stand up to that kind of abuse? Looking for quality with good specs.

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I prefer to use a lead acid battery in vehicles that came factory with it. I've got a factory sized battery from O'Reillys. https://www.oreillyauto.com/detail/b...4742480?pos=15

I just put a interstate MTP-24F in

750cca and 130RC.

It tested at 770cca with my MidTronics tester.


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