Power door lock system — description and check
1. A power door lock system operates the door lock actuators mounted in each door. The system consists of the switches, actuators, the Body Control Module and associated wiring. Diagnosis can usually be limited to simple checks of the wiring connections and actuators for minor faults that can be easily repaired.
2. Power door lock systems are operated by bi-directional solenoids located in the doors. The lock switches have two operating positions: Lock and Unlock. When activated, the switch sends a ground signal to the door lock control unit to lock or unlock the doors. Depending on which way the switch is activated, the control unit reverses polarity to the solenoids, allowing the two sides of the circuit to be used alternately as the feed (positive) and ground side.
3. Some vehicles may have an anti-theft system incorporated into the power locks. If you are unable to locate the trouble using the following general Steps, consult a dealer service department or other qualified repair shop.
4. Always check the circuit protection first. Some vehicles use a combination of circuit breakers and fuses.
5. Operate the door lock switches in both directions (Lock and Unlock) with the engine off. Listen for the click of the solenoids operating.
6. Test the switches for continuity (refer to the wiring diagrams at the end of this Chapter).
7. Check the wiring between the switches, control unit and solenoids for continuity. Repair the wiring if there’s no continuity.
8. Check for a bad ground at the switches or the control unit.
9. If all but one of the lock solenoids operate, remove the trim panel from the affected door (see Body) and check for voltage at the solenoid while the lock switch is operated. One of the wires should have voltage in the Lock position; the other should have voltage in the Unlock position.
10. If the inoperative solenoid is receiving voltage, replace the solenoid.
11. If the inoperative solenoid isn’t receiving voltage, check for an open-circuit condition in the wire between the switch and the Body Control Module, and between the lock solenoid and the Body Control Module (see the wiring diagrams at the end of this Chapter).