I tested for a key off battery draw and have a constant 5 amp draw (varies from 4.89 to 5.22) with the key out of the ignition. I found this draw at the smaller battery cable that feeds the under hood fusebox. I have pulled every fuse (incl. large 30 and 40 amp ones) and reading on ammeter does not change. I temporarily installed a disconnect in the power lead to fusebox that I shutoff when I am not going to be using truck for a while. all is fine with this disconnect "off", batteries have been fine since. I have disconnected (3) non factory installed items (Edge, fog lamps and lighted nerf bars) to rule them out of equation. Any ideas?

 

Don't know for sure, but I assume there is some constant voltage to the instrument cluster, stereo and probably ECM or control modules. Doors unlock with remote, Odometer lights when door opened, interior lights come on, stereo maintains programming, etc. All of these things with no key in ignition. Something has to be monitoring for door open, alarm off, etc.

 

Sounds like you are doing it right by pulling fuses and measuring draw. I have a separate fuse for my FASS, did you check that. Is it possible to have an internal battery short since it's only on one battery? Maybe switch batteries and leave the other disconnected.

Pete
(xploretx)

 

it is not the battery. if the draw leads to the pcm or ecm, check the leads leaving the module to see if it is being drained within the module