Check engine soon light on 2001 GMC Yukon XL 1500

Check engine soon light just came on. Vehicle passed emmisions testing last month. Disconnected battery cable srest light. Light came back on. Autozone tried to read code but no indication. Stated that that is a blown fuse. Any idea where to start?

Asked by for the 2001 GMC Yukon XL 1500
the fuse is the same as cig lighter fuse replace that first then read code