2011 Tahoe no crank no start need help

mikez71 said:

You can crank it with the scanner, but not the key?

Bad ignition switch?

Click to expand...

Rockman101 said:

Fixed the wire didn't fix the problem, but I checked my ignition wire under column while cranking it drops to 0 volts. When I let off back to 12.5 volts? Red with white stripe wire. So something is pulling down the network??!!

Click to expand...

j91z28d1 said:

do you know where that wire is getting it's 12v from? I'd guess a fuse? I'm not in front of my software to take a look. but I've heard of fuses getting bad connections in the fuse box, soon as they get a load it drops off?

Click to expand...

Rockman101 said:

Fixed the wire didn't fix the problem, but I checked my ignition wire under column while cranking it drops to 0 volts. When I let off back to 12.5 volts? Red with white stripe wire. So something is pulling down the network??!!

Click to expand...

j91z28d1 said:

so I looked back at the ign switch diagram. I'll upload.

I look at these diagrams kinda often and I'm not really sure what's going on here. so first that red wire with a white strip. if this is right, fuse 35 from under hood box 2amp. constant power to the ign switch and theft module. I don't believe you should see power drop off it while in acc, run or start.

looking at the ign diagram the right side, I'm not sure what all is going on. maybe some other guys can see it better. white wire pin 6 is 5v from the bcm. pink/black is the ign control/command to the bcm, but key in switch is there too. so looks to me like key in but off position it sends 12v to the pink/black. once moved to run it connects the 5v white wire to the pinkblack and then when moved to start it connects the 5v thru a resistor to the pink/black. dropping 5v to 3v maybe?

I'm mildly confused by why it's doing that or if I'm seeing something incorrect. but either way, I say all that but check for 12v at fuse 35 under the hood while in start and see what happens. if you keep 12v move to pin 4 of the ign switch and look for 12v while trying to start there.

the rest of the linked internal switches. acc and run it sends 12v to theft; yellow pin 2, transferr case; blue pin 10, tranny; blue pin 9, and ecm; blue pin 18 of connector X1


in run and start it sends 12v on pink to bcm so the bcm knows to turn on the run/crank relay under hood.

Click to expand...

Rockman101 said:

Thank you very much, i'll check these out tomorrow. It's almost like when radio HVAC lights all cut out when in crank position.

Click to expand...