1. Remove the rear door unit.
2. Remove the screws, then remove the rear door latch and lock actuator.
3. Install in the reverse order of removal.
Mazda 6 Service Manual: Operation
NOTE
The engine may not start and security indicator light may illuminate
or flash if the key is placed in an area where it is difficult for the system
to detect the signal, such as on the dashboard or in the glove compartment.
Move the key to a location within the signal range, switch ...
Mazda 6 Service Manual: Dual proportioning valve replacement (without abs)
1. Remove in the order indicated in the table.
2. Install in the reverse order of removal.
Dual Proportioning Valve Installation Note
Install the dual proportioning valve so that the R mark faces the left side
of the vehicle.
...