Went to start the truck and it acted like the battery was dead. I checked DC battery voltage it was 6.5 volts. I removed the positive terminal and the voltage went to 12.5 Volts. Hooked up good jumper cables and the dome lights are bright now. I put the key in and real quick a no fuse light flashed on the odometer display. I turned the key and all the gauges pegged out and quickly went to zero.Then I turned the key and the starter began turning over but the truck won't start. The check engine light has been on for a week now just no time to get it tested. I found 3 fuse blocks and all fuses are good. What could be the problem?

Your battery is shot to start with...

It won't even drop anywhere near that while cranking on a cold winter morning.

The rest we can't guess without knowing what codes are in the computer... and with a check engine light... there ARE error codes in it.

. Install a new battery, being sure to get it fully charged first. Clean the battery terminals and cable connections thoroughly.

. Check all under hood and under dash fuses with a test light or multimeter.

. Attach a code reader to the DLC and check for codes.