The first thing you should do is verify if the problem is with the vehicle or the code reader. Try another code reader to see if it also will not communicate. If non-communications persist then do this:
- Check for a blown 10 Amp fuse in cavity 11 of the junction block
- Check the 40 Amp fuse located in cavity 5 of the Power Distribution Center (PDC)
- Check the case ground attached to the rear of the radio
- Check the 10 Amp Ignition Off Draw (IOD) fuse located in cavity 10 of the Power Distribution Center (PDC)
If this all checks out good, then you will have to verify all power and ground circuits AT the Powertrain Control Module (PCM) connector and verify continuity on the wires between the data link connector and the PCM. If it comes down to this, post a reply to this solution and let me know. I can provide step-by-step instructions and wiring diagrams necessary to accomplish this.