So on my way to work this morning my check gauges light came on and my batt. gauge went all the way down to 8 volts. I parked it, shut it off, and tried to start it agian and it started just fine. Went out to it after work and tried starting it and the batteries were completely dead. Popped the hood to jump it and it looked like the grid heater were on for hours. Intake horn is black, stuff is melted, im not happy. So i thought a relay stuck on this morning and drained my batteries and almost burnt my truck to the ground right? Well i jump started it, disconnected the grid heater relays and went home. 20 minutes after driving the volts went back down to 8 and when I shut it off and try to start it agian it cranks over just fine but take about 10-15 seconds to start. I have a 2502 and 2509 code.
Anyone have any ideas on were to start? Thanks Jake

 

You probably know, but those are codes for intake air heater, and charging system.

It might not hurt to disconnect both batteries, let them sit overnight, and see what kind of voltage reading you get. If one is 12v and one is 9, you may have a battery with a dead shorted cell.

Sorry I can't be of more help.

 

Thanks for the input. Tonight I cleaned every connecton, batteries, grounds, alt. they all seemed fine but I drove it about 20 miles and no problems yet.

 

With the grid heaters disconnected you will always get the codes for them. You may need a new ECU along with new grid heaters.