P2509 Won't Start

[TMRoper1669]

Haven't ran my '08 Mega Cab for a week or so, went out to take it for a drive and nothing. Put the battery charger on it and batteries were dead, no problems at all with electric accessories before so why now. Finally got it running shows to be charging at 13volts or so, took it for a drive with lights and all electronics on and ran fine got home waited for an hour or so and started fine any ideas. I have never had any problems with it sitting for a week or so without driving.

 

[HBarlow]

Only current draw could cause it. Something was drawing down the batteries while it was parked. The OEM system has clocks and other devices that draw tiny amounts of current but I wouldn't expect them to run down the batteries in only a week.

The usual suspect, interior lights have to be ruled out on the newer trucks because a timer will shut them off after a time, even if doors are left ajar. I would suspect an aftermarket add on of some kind.

The sure way to determine what caused it is to disconnect both batteries and connect an ampmeter set on low scale between the positive post of one battery and the positive cable. If current draw is indicated, something is drawing current.

Determine what by slowly pulling fuses one by one until it stops drawing current.

Is it possible that the batteries were a bit low from lots of short drives and it was parked for ten days not just a week?

 

[Hoefler]

You could just have a bad battery, have them both tested.