Description and testing of the central door locking system (BMW 5 Series E28)

The central door locking system operates the door locking actuators installed on each door. The system consists of switches, actuators and wiring. Diagnostics are limited to a simple check of the wiring and actuator contacts for minor damage that can be easily repaired. Such checks include:

• Checking system fuses and/or circuit breaker (where is it available).
• Checking the switch wires for damage to the wires and loose contacts. Checking the switches for conductivity.
• Remove the door trim panel(s) and inspect the actuator wiring connections for looseness or damage. Inspect the actuator rods to ensure they are not bent or damaged. The actuator can be tested by briefly connecting battery power. A loud click will indicate that the solenoid is operating properly.