To troubleshoot a Ford Ranger, first diagnose the issue. Check whether shifting of the four-by-four system to a high position is possible by pressing the corresponding button. The four-by-four and the dash button should illuminate.
If the buttons do not light up, the shift motor, the four-by-four module or the dash button may be faulty. To check which component has the issue, press the four-by-four button and to listen for any sounds in its relays. If you hear a distinct sound in the relays, it indicates the issue is either with the relay module computer or the shift motor.
One of the most common problems that occurs with a Ford Ranger is a broken stop bumper in the shift motor. To diagnose any problem with the four-by-four module, disconnect the two connectors connected to the left portion of the module and turn on the car. Press the reset or test button, and check whether the LEDs flash four times. If the LEDs continuously flash or do not flash at all, the issue is with the module.
If the four-by-four module is working as expected, check the switch, the magnetic clutch or the wiring harness for any damage. If the vehicle makes noise below the front wheels, check whether the hub locking is correct.