New member- looking for help with code U0109 (no comm to FSCM) and overnight battery drain on my 08 Sierra

[DJPepper]

Hi folks, I've got a problem with my truck that I'm hoping someone can offer some guidance on. I've researched the conditions and search some forums but haven't found anything yet.

 

So 3 mornings ago I went to drive my truck and the battery was dead. I tried jump starting it and it turned over fine but wouldn't fire. It was cold in Northern Michigan so I thought I might have some bad gas and freezing in the fuel lines. I pit a heater on it the next morning and tried starting and the battery was dead again. I charrged it again and pulled a U0109 code. And others related to low voltage (those have cleared and not returned since not letting the battery die). So I haven't seen anyone have the battery and u0109 occur at the same time. Hoping someone has experience with the conditions simultaneously and can help track down the problem.

There is power at the fuel pump when I bypass the fscm at the plug. I've also tried a paraitic draw test by measuring voltage drop across fuses and nothing turned up. But when I put my ammometer in line with the battery ground I get an initial draw of about 2.4A that starts decreasing after 30 seconds and stabilizes at 20mA.

Any ideas would be greatly appreciated!

 

08 Sierra 1500 SLE 5.3L 4x4 with no mods and no sign of issues before this happened