The power door locks in your Ford Ranger are activated by a switch-controlled solenoid (called an actuator) connected to the latch mechanism inside the door by a steel rod. By changing the polarity of the voltage supplied to the solenoid, the door can be locked and unlocked using the same actuator. Troubleshooting this system requires the use of basic testing skills and equipment. An experienced home mechanic will typically complete this task in about an hour.
Remove the small, round, plastic screw covers located below the door pull in front of the arm rest using a small pick to pry them out. Remove the two screws located behind the screw covers and the one screw on the bottom edge of the door near the speaker grill, using a Phillips screwdriver.
Grasp the lower edge of the door panel with your hands and pull out to unclip it from the door. Lift up on the panel to unhook it from the top edge of the window frame and unplug the speaker, power window switch and the power door lock switch if equipped. Lay the door panel aside.
Clip the battery clip ends of the automotive circuit tester cable to the battery terminals in the engine compartment. Test for ground at the wiring harness side of the switch's electrical connector by touching the probe end of the tester to the terminal inside the connector. The black wire on either switch should be ground at all times and will turn the tester's green light on.
The pink/yellow and pink/light green wires should be power when the switch is not activated and will turn the tester's red light on. Replace the lock relay if pink/yellow indicates no power and replace the unlock relay if the pink/light green wire indicates no power.
Plug the switch into the electrical connector. Unplug the door lock actuator electrical connector. Test the wiring side of the connector for ground on the pink/black wire and the pink/orange wire. Both wires should be ground when switch is not activated.
Test for power and ground during "Lock" signal at the actuator. Activate the switch in the "Lock" direction. Test the wiring side of the connector for power on the pink/black wire If ground on the pink/black wire switches to power when the switch is activated to lock the door, replace the actuator. If ground does not switch to power, replace the switch.
Test for power and ground during "Unlock" signal at the actuator. Activate the switch in the "Unlock" direction. Test the wiring side of the connector for power on the pink/orange wire. If ground on the pink/orange wire switches to power when the switch is activated to lock the door, replace the actuator. If ground does not switch to power, replace the switch.