Data link connector not working. Scanner says tool not plugged up!

Try checking the power and ground terminals at the OBD connector. Connect a voltmeter between terminals #5 and #16 and you should have battery voltage. Search "GM OBDII connector pinout" and you will find pictures of the terminal locations.

The fuse on my 2004 Tahoe was blown for cig lighter and code reader. They use the same fuse. Check fuse!

well hopefully you alredy got it fixed i got the same issue and belive it or not ,sometimes when the cigarrette lighter fuse goes out the obd2 port wont work on the tahoes, 15amp blue. both of the answer above are absolutely correct!

samething with a 2000 ford explorer

Check your cigarette lighter fuse it has the power to your data link connector