Hi i have a big problem with my tahoe, it won't start at all, the fuel gauge is below empty and the message center is blinking between "Battery", "Security" and "Low Fuel". i have a full tank of gas and i have been trying like mad to find something regarding this but no luck, so i hope someone here have an idea.
all i figured out so far is that the +12v from the PCM to the Fuel Relay isn't there when i turn ignition to ON but if i pull the relay out it i can read the +12v from the wire. If i use a wire from the battery + i can get the fuel pump to run.
I have tried using a scan tool to try and read out DTC but it won't even establish a connection even though i used to be able to do so its a 2001 tahoe

 

Have you checked the wiring to the ignition switch?

Also check the interior fuses
Chevrolet-1500 Pickup: OBD II Device - No Power ; Automotive

My OBD Scanner won't work! - Chevy Truck Forum | GMC Truck Forum - GmFullsize.com

 

The pcm is offline and the cluster gets all of that information via the serial buss from the pcm. Start checking fuses verify all pwr and grd at the pcm with the key on is the place to start. Check the grounds at the back of the cylinder heads on the dr and passenger side tug on the wire to verify it is solid and not broke in the insulation there are another set of grounds on the drivers side of the block behind the PS pump.