check engine light on 2003 Chevrolet Express 2500

My check engine light would sometimes come on in the winter. This last winter it did not. Now it came on about a week ago. I went to autozone to have them pull the code and the instrument say it must be connected to vehicle. I'm trying to figure out why it won't read the code.

Asked by for the 2003 Chevrolet Express 2500
I would recommend a proper diagnosis be performed by a qualified technician, not a clueless parts store trying to sell you parts based off of a code pull...that they apparently aren't capable of doing.

It's possible you may have a blown data link fuse?

In any case, check engine lights can come on for many reasons, and only a true diagnosis can get to the bottom of the problem.
It wouldn't read because the fuse for the lighter was blown. Go figure. Anyhow it was a p0442 which is with the evaporative system. Thanks for tryiing
Yes, the lighter fuse is also what powers your data link. So - indeed so.

P0442 - yes, have your evap system diagnosed.