Hey I have a 08 rx8 grand touring with 51k miles Recently my battery went bad and I had a CEL. I got the battery charged and the battery light and CEL was still on and it wasn't idleing normally so I changed the battery. When I did that the CEL went off so I figured it was from the bad battery but the battery light was still on I figured that would reset or something. Then when I turned it on again and recently the CEL went on again with the battery light still on. Before I get the CEL checked does any one know if maybe the new battery isn't giving enough crank power and causing the CEL. Because I just took the old battery to one of those battery stations that trade batteries for a small fee so I don't know what the specs on the battery is.

 

Your alternator is probably crapping out. Its not charging your battery so youre having problems starting it. I dont think the ecu throws a code for the battery. It would have to be your alternator. Have you noticed if your power windows go up slower than normal?

 

just a little, its more like when I put the windows up and its almost closed it kinda sounds like the motor is struggling the last inch to get it all the way up.

 

If the battery light is on it's most likely your alternator. If you take it to an Autozone or O'Reilly's most of them have a machine that can test alternator output while it's still in the car.

 

+1 on that ^. Also have the battery load tested.

 

+1..

 

Hey guys I will take the car to autozone Tuesday, I am pretty sure you guys are right about the alternator because its idleing the same way as before with the old battery. It drops rpms for a second then picks it back up like it is not getting enough power to idle and this is a new battery.