Recently lost my 4WD when shifting it from 2WD to 4WD. I have electronic shift dial on the dash. I've replaced front diff Encoder motor, T-case Shift motor. Last week after I swapped the Tcase motor the 4WD worked again for about 2 days. Now its out again. Ran codes on it today at Oreilly's and its got CO 387 and CO 374. Looks like the 374 is a 4WD speed Sensor? and that failing is throwing the other code 387? Any ideas on what the root cause would be?