I have a 2002 for explorer 4x4 limited model with a 4.0L non flex fuel. The 4wheel drive is not working. The push botton on the dash shifts through 4wd hi and low and auto but has no 4x4. It has a code for P1812, I cleared the code and replaced the 4wd control module I was told this controls the clutch in the transfer case and this has not fixed the problem. There is no noises from the transfer case. Any Idea where to go next?