Hello all members and thanks for having me.As most who join I am having a problem I can't solve and looking for help getting a Cat 3126 w/allison auto in a 2001 T7500 GMC back running.Truck has 2 battery set up with master switch.Was running till one battery gave up and wouldn't start.We disconnected bad battery bypassed master switch.2 min later generator started smoking.We removed power wire from generator and truck started and we got it back to shop.Next day installed new batterys and generator and now we have a no crank, no power to instrument panel condition.I had Cat check the PCM,they said good.I have power to the 2 unstitched power pins 52 and 53 to PCM.I am not getting any power to pin 70 with key on.I have power at all fuses in the 40 amp and up under hood panel.I have power at the ignition relays but there is no signal telling them to close or work when key is turned.I have power to the cab fuse block on everything except # 6 that controls all the relays and powers instrument panel also I believe.My head is spinning at this point and getting close to calling a wrecker to take to a repair shop.I feel there is a engine shutdown system keeping everything from working as I can get it to crank if i remove the ignition fuse in the cab and use a jumper wire in its place the truck will crank indicating key switch, starter and solenoid are good.Also the day light running lamps don't come on when key is on but the headlights, turn sigs, horn,cab interior light work.Any input would be appreciated.Thank you all

 

I found connections at Ignition fuse were loose.Repaired that.Truck will now crank but no start and no power to Instrument panel .Replaced key switch with known good one also but didn't correct problem.