When I installed dual batteries I screwed up and allowed the evap hose (the evap controller is relocated slightly with the removal of the stock batt box) to lay against the egr pipe - it melted through and the check engine light came on. The info center would not show the code (just the five dashes and done as you describe) so at Ronjenx's advice (that not all codes will display) I bought a reader - and when it showed "unexpected egr flow" that put me looking at the hoses where I found the problem. Worthwhile investment at 80- as the dealer certainly would not have covered either diagnostics or repair!
Check all of your evap lines for kinks, melts etc - but get the reader - it WILL pay for itself in no time!
J Wm Bishop EA, ASADE
14 XTS V, 12 JKS, 11 JKUR, 11 SNSKR 31, 04 GTO, 02 DTS, 57 Chev3100, 56 VSG.