Check the fuse for the 4WD computer. It is located in the driver foot well fuse box. If the fuse is blown the lights do strange things.
Easykill had the same problem on Saturday - turned out to be the vacuum pipe to the manifold was disconnected. Check the pipes as they could have a leak. Also put your finger on the solenoids and get someone to switch to 4H and 4L if they are working you will feel the “click” - engine must be running.
The solenoids are located on the driver side of the engine bay half way to the front – if you can’t locate them I will get Easykill to take a photo and post tomorrow morning (he is working late shift this week)
Good luck
Dingo