On a vehicle with electric locks the process is a bit different.
Car door lock actuator circuit.
When the actuator fails or starts to fail you ll likely notice one or more symptoms that make your daily commute less pleasant.
If there are no external door lock switches you will most likely have a vacuum type system or an aftermarket door lock system with relays or have an added actuator that needs relays.
This manipulates a series of rods that slide back and forth opening and closing the locking mechanism at the door latch.
When the actuator moves the latch up it connects the outside door handle to the opening mechanism.
On manual locks the locking function operates by pushing or pulling on the door lock.
In some cars the door lock actuator is positioned below the latch.
A rod con nects the actuator to the latch and another rod connects the latch to the knob that sticks up out of the top of the door.
The concept of a door lock actuator works great until it doesn t.
Next with your multi meter probe each of the wires in this harness and write down the readings during lock unlock and at rest positions of the switch.
In this car the power door lock actuator is positioned below the latch.
A rod connects the actuator to the latch and another rod connects the latch to the knob that sticks up out of the top of the door.