Shifting into 4LO

[06 SUT]

I got a Service 4WD notice on the DIC but no DTC when I hooked up a scanner. Now the truck will not shift into 4LO locked. It shifts fine into 4HI locked. I only have a partial service manual that does not include a troubleshooting tree for this. Any one out there have a good starting point before I have to take it in to the dealer?

Thanks

[HUMTECH]

Does your scanner read chassis and body codes? Most dont unless you spend some money on them and get a good one. Tcase codes wont show up if just reading powertrain systems

[06 SUT]

Thanks, that being said, obviously mine does not. It is a standard performance tuner/scanner.