If anyone can help figure this out it would be greatly appreciated. I have a '98 Expedition w/ 4WD. The transmission shifts through all four gears but won't go into O/D. The shifts occur too quickly and the O/D light on the shifter **** begins to blink after the second stop-and-go cycle. At 40 MPH (top speed) the check engine light does not come on but the engine over rev code along with P1729 - 4X4L switch open/short code sets. I retreive these two codes with my Solus Pro scanner. While checking the Generic Module PIDs I confirmed that all 4WD selector switch positions are acknowledged but the transfer case contact plates A, B, C, & D all indicate exactly opposite of the truth table I printed from ALLDATA. Example: 2H reads A-Open, B-Closed, C-Open, D-Open on my Solus Pro, but ALLDATA's truth table shows A-Closed, B-Open, C-Closed, D-Closed. Question: Is the 4x4L Switch the same as the 4WD selector switch or is it something/somewhere else. If there is a short or open in the switch I should be able to find it easily, but everything I have checked so far (with the exception of the contacts being opposite) seems to be fine. All information/personal experiences on/about this problem is welcome. Thanks!