Just came back from my first Emissions in AZ for my 2019 Tahoe Premiere. It failed stating there was no Voltage at the Data link connector. (OBD) They tried two different machines there. They said it would show as connected and then lose it. Any idea what I need to look for to fix this? Thanks!

 

Check your fuses first.
You should also read your warranty. Emissions equipment is guaranteed for a long time.

 

Check the fuse labeled "Cigar"; it's for the cigarette lighter sockets.

Same issue happened at Arizona emissions with our 2005 GMC Yukon, emissions testing could not connect to OBD2 socket, and of course emissions folks had no idea why. So Mrs. Cusser had to drive home, I had to figure out that the "Cigar" fuse was blown, and replaced that to fix. Then she had to drive back for a second test. Of course some folks there knew the problem.

Oftentimes a coin falls into such lighter socket and shorts the fuse.

Since your vehicle is 5 years old now, AZ Emissions has to get its $$$. Federal emissions warranty covers catalytic converters and engine computer for the first 8 years or 80,000 miles (whichever first occurs). Maricopa and Pima counties emission-test all the way back to 1967 year, stricter than California, with no emissions testing in the other counties. And no safety inspections.