MAVERICK2525

Hi to everyone, I have a 2006 2.8 Grand Voyager nice motor, pulls my caravan very well. I do have a problem with battery draining , just replaced battery but still draining it in a short distance , a sign comes up on the radio screen, asking me to start the engine (although already running) will shut down the system in 3 minutes , could this be due to the radio amp ?if so where is it and how do you get at it . Thank you in anticipation .