I have had to replace the 2 batteries in my 2005 PS 6.0L Crewcab today since at least one of the batteries is dead. Put 2 new batteries in and when I tried to start the truck the alarm goes off. I tried to mess with the key fob but that did not do anything. Tried to start the truck but it would not crank over. The dashboard light was flashing while the alarm was honking. I ended up disconnecting the passenger side battery to make the alarm stop. I appreciate it if anyone could tell me how to reset the alarm.
Right now I have reconnected the batteries and the alarm is not sounding as long as I am not trying to start the vehicle.

Many thanks for your help!