Unable to read OBD2 scanner.

[adriver]

SO THIS IS FOR MY 02, and 02-03 they had the most changes in the NBS model. I can not confirm if this is the same as yours or not.




The wires might be the same. You should be able to see which pins are use, and find the wire color behind the pins. If they match up as this, they are probably the same.
(You could always spend the $10-$20 on ebay, and buy the service manual for your vehicles (2003 tahoe, pdf service manual on ebay. Its about 10K pdf pages of everything. 3K pages on the engines, 800 pages on the brakes, all the torque specs, repair and diagnostic procedures, parts diagrams, all schematics, and pinouts. IMO, EVERYONE that works on their vehicle should have this. This was the set of 3 or 5, 3" thick manuals the dealer got, and now available (legally) in pdf).

I would use a test light to verify grounds and battery voltage and CL2 serial data. Could use a multimeter for batt voltage. The CL2 serial data is every module in the engine bay that has a voltage reading. If any work has been done in the engine bay, most of the wires are incredibly small, and brittle. I myself have broken the strands, but the casing was fine. If anything under there has been changed or replaced, look for fraying, kinds, bends, any damage along those wires.

The grounds are always suspect if you live in a snow/salt/rust area. You may have dirty grounds that need to be cleaned up and interfering with the voltage reading you should be getting.

 

[The guitar zombie]

You seem pretty novice to this. Not listening is going to make it even harder. The mere fact that this vehicle sat for 3 years with gas in the whole fuel systems explains plenty why the engine is running so bad. I personally would yank the fuel filter out (if equipped) and drain the tank jumpering the fuel pump wire at the OBDII port terminal or pulling fuel pump relay and jumper it there. That bad gas in there isnt going to get better unless dilluted enough with good gas and likely alot of octane booster at the very least. Its easier just to get rid of it.

Hi, thanks for your efforts. The Yukon runs great now, replaced plug wires and found a funky one. But I checked grounds, tried another reader and as a reminder, my reader did a successful battery check. I checked all the fuses and now there may be nothing left but to fear the worst. The only other thing that I can say was weird, was the gas guage worked intermittently.