Mazda 6 Service Manual: No.4 hard to start/long crank/erratic start/erratic crank

No.3 will not crank

No.5 engine stalls-after start/at idle

Other materials:

Mazda 6 Service Manual: Rear door lock actuator inspection
Door Lock Actuator 1. Disconnect the front door lock actuator connector. 2. Apply battery positive voltage to the front door lock actuator terminals and inspect the operation of the front door lock actuator. If not as specified, replace the front door lock actuator. With double locking ...

Mazda 6 Service Manual: Antilock Brake System (ABS)
The ABS control unit continuously monitors the speed of each wheel. If one wheel is about to lock up, the ABS responds by automatically releasing and reapplying that wheel's brake. The driver will feel a slight vibration in the brake pedal and may hear a chattering noise from the brake system ...