I had my batteries die on me to I recharged them on 6amp which took about 24 hrs a piece. Tried to start truck and ran fine. Less then a week later, same thing, batteries dead. Rechanged again, disconnected my amp for the radio and Now a code P2509 (ECM/PCM power Imput Signal Intermittent). Further, now my horn goes on and off at will. I had to find a new horn as the old one had gotten a hole in it. Any help would be appreciated as I need my truck to work correctly. Thanks

 

Check the fuses ALL the fuse's also I believe there's a rather large fusible link from alt. to pass. side batt.

 

Check the voltage while running. Should be above 13.5V up to 14.5V, if you are not within specs, you should check the alternator.
how many miles? Worn brushes?

 

Check the alternator as described above.

If thats ok, pull the batteries and have them load tested at Autozone etc.

 

Yeah more than likely you either have a dead cell in a battery which will kill both when sitting idle. Or you have a faulty alternator that is not putting out enough voltage to charge the batteries.

Make sure if it is the batteries that you have the alternator checked also. Sometimes a bad battery will also hurt or fry an alternator in the process.