My 2000 Yukon XL 4x4 1500 won't shift into 3rd gear. Everything was working fine, we went into a store and then when we left, no 3rd gear. The tranny fluid is full and I don't see any leaks. I have tried all gears on my column shifter but it won't go from 2nd to 3rd. There has been zero noise, difficulty shifting or any other indicator that there may be a tranny issue leading up to this. It shifts perfectly from 1st to 2nd but that's it. Reverse works fine also. I took it up to about 80km/h (50mph) at 3500rpm-4000rpm but no shift. When I let off the gas, there is no engine braking either, almost like I am in neutral. I hooked up my OBD2 and the only code I got was P0440 (EVAP control) which would not be related to my transmission issue. I think it could be a A/T control solenoid, but any other thoughts? Any idea how to confirm/rule out a solenoid? Thanks in advance for any help!