1. Disconnect the negative battery cable.
2. Remove the intake maniforld.(see INTAKE-AIR SYSTEM REMOVAL/INSTALLATION.)
3. Remove the PCV valve.
4. Blow through the valve and verify that air flows as specified.

Specification

Egr valve inspection
Three-way catalytic converter (twc) inspectionMazda 6 Service Manual: Front drain hose installation
Caution
If the front drain hose is pinched or bent anywhere, the water in the hose
may not discharge and enter the inside of the vehicle. During and after
installation of the trims and the headliner, always make sure there is no
interference with the front drain hose. Fix any problem if found ...
Mazda 6 Service Manual: Foreword
Caution
When the engine does not start or stalls and the following DTCs
are not indicated, go to engine symptom troubleshooting.
Note
When the immobilizer system is defective, the engine cannot be
started.
If engine condition is normal but light stays on, inspect for
short circ ...