03 Tahoe dies & battery light comes on

[Tonyrodz]

Any wet brake lines or puddle underneath?

 

[Jarrid]

I'd say replace your tps sensor had same symptoms cleared mine up in 01 Tahoe ls

 

[mizzouguy]

Is your master cylinder full of fluid? Pedal to the floor sounds like a leak or bad booster...unless its hydroboost.

 

[M1Gunner]

Start the vehicle up and with it in park idling, jiggle the key. It's very possible you ignition lock cylinder is worn and causing the ignition switch to have problems which would in turn give all the symptoms you're having.

Except the pedal to the floor. That is gonna have nothing to do directly with the electronics.
Pedal to the floor but no brake fluid leak visible is more than likely an internally leaking master cylinder. Which with the age and mileage is not uncommon.