Greetings everyone.

I'm having a real time with an 03 Tahoe 5.3, Z VIN, and was hoping I could get some assistance in trying to diagnose the issue.

Here's what I know so far. Thank you in advance.

What is known:
-99% of the time it will not crank - every once in a while it turns over and starts right up, can drive it all day as long as I don't turn it off.
-I can always know when it WILL crank, because the chimes will sound when I turn the key to ON, and the fuel gauge will register the fuel level.
- I can always know when it WILL NOT crank because there will be no chimes, and the fuel gauge will do nothing.
- With the key still ON, the CEL, ABS, and Low Fuel Light (when the chimes are not present) are more dim than the Parking Brake, Security, and Battery Lights.
- If I tap on the brakes, these lights get a bit brighter.
- This is a new battery
- I can 'jump' the starter relay in the fusebox (30 & 87) or jump from the relay to the positive terminal and it will crank, but it sounds dry like no fuel is being delivered.
- I have checked the pertinent ignition, crank, pcm etc fuses and all are intact.
- Security light is not flashing or staying on, so I assume it is not a passlock issue, unless that's what I'm dealing with when I try and jump the relay.
- At this time I am unable to hook a scanner to the obd2, as it says there is no communication. Cigar Fuse appears to be intact as well (I've heard it was connected to PCM in some way), however none of the other outlets function at all since I bought the vehicle.

I know a common suggestion is a grounding issue, but what I can't seem to find is which ground point I should be focusing on.

Anyway thanks again and I'm really hoping I can get this figured out. I'm in a bit of a pickle here as I live 2 hours from ANYWHERE!

I'll gladly buy a case of Beer or a Pizza to anyone who can help me get this back running.

 

First things first, Do you deliver? Just kidding !

A good part of the time, from the symptoms you provide, It sounds like there is a loss of power either to or from the ignition switch to the items/components the switch normally provides power to.
When you jump the start relay it still does not provide power to the PCM which controls operation ofi the fuel and injector system. That is why I believe the engine cranks over, but the engine doesn't fire up and start. You are probably right when you believe it is not getting fuel.
What you might consider trying is to see if you are getting power to the ign sw all the time and the ign coils when the key is on. This can be easily verified with the use of a test light. Let us know what you find, OK, thanks.?

 

Hanky, Thanks for getting back to me. Yeah I figured I'd send paypal, gift card, or heck nowadays I could order it and someone could do curbside at their grocery store... I just really want to get this resolved and if it were a neighbor I'd do the same so why not do it here?

Yes as I understand it there are some contingencies that have to be met to get fuel and the starter relay to cycle on.

I do have a test light, but am I looking for the ign switch / ign coil Fuses, or the actual components on the vehicle? If fuses, I'm having a little trouble deciphering which ign fuse is which? Other than the ign fuses in this diagram, there are two more 40a ign fuses (ign A & B) above the starter relay.

 

$30 will get you a 1 yr subscription online shop manual with wiring diagrams at alldatadiy.com. I have subscriptions for every vehicle in my ''fleet''. Only way you will be able to trace out power flow and see the right test points and grounds is with a manual. It's technician intense but when it comes to electrics you need the ''road map''.

 

"I can always know when it WILL NOT crank because there will be no chimes, and the fuel gauge will do nothing."

Am I understanding that the main issue is that most times the key switch will NOT crank/spin the engine? Because that could be the electrical part of the ignition switch, different circuit for "Start" than for "Run".