OBD2 power but no communication

[Ian Mills]

I'm beating my head against the wall on this one, any help would be appreciated.

A buddy of mine has a 06 CCSB Sierra 1500 SLE2 (8th vin T). It threw a CEL and when we plugged in a code reader to diagnose the problem it powered right on, auto-detected the make and model, and then froze at 23% progress. I tried it on multiple other vehicles and the reader seems fine. I took my multimeter and checked the pinouts and sure enough 4 and 5 were grounds, 16 was 12.5 volt constant, and 2 had about 11.5 volts. Plugged the reader back in and same experience. I don't know if that 1 volt difference is to be expected or not.

My buddy took the truck to a shop with a snap-on scan tool and apparently they had no issues connecting with that. The issue was a bad cam position sensor which we fixed and tried the reader again. Still nothing. We also tried borrowing a scanner from a local parts store (oreilly's) and theirs did the same thing mine did.

Any ideas?

EDIT: I don't know the significance of the 23%, but that's where it stopped every time. I figured it might be the start of communication with a particular module or something

Edited December 17, 2020 by Ian Mills