I have an 04 CTT and it was running OK until this morning. It decided to not crank. Radio, lights, and display panel were on. I know I have to check the battery. I would like to know which battery starts the car. I know I have two batteries in my car. Most people seems to pay more attention to the one under the driver seat. However, there is a link said the one in the trunk starts the car. Which one is this? Thanks for any suggestion.
ALX5

 

I believe there is only one battery the connection under the hood is just an extension for jump starting