encoder motor

how do you test the encoder motor to see if its good or not cause my 4x4 doesnt work sometimes 4x4 low always works but its a pain to get it in 4x4high then back into 2high..........(lights flash when fails to work

if 4x4 always works, your encoder is working normally. I would look to the vac switch on the transfer case and check the vac actuator underneath the battery tray for leaks/tears.