1. Remove the clamps and vacuum hose.
2. Apply both suction and pressure to the engine-side hose, and verify that air blows only toward that side.

Air bleeding
Brake pedal inspectionMazda 6 Service Manual: Front/rear abs wheel-speed sensor inspection
Visual Inspection
Remove the wheel and tire, and inspect the sensor for looseness and damage.
Replace the sensor if necessary.
Clearance Inspection
Inspect the clearance between the wheel-speed sensor and the sensor rotor.
Clearance
0.3-1.1 mm {0.012-0.043 in}
Resistance Inspection
...
Mazda 6 Service Manual: Indication on Display
The Distance Recognition Support System (DRSS) operation status is indicated
in the active driving display or multi-information display. Regarding malfunctions,
check the vehicle conditions or have it inspected by an Authorized Mazda Dealer
according to the content of the displayed message.
R ...