Mazda 6 Service Manual: No.3 will not crank

No.2 mil illuminates

No.4 hard to start/long crank/erratic start/erratic crank

Other materials:

Mazda 6 Service Manual: Drive Selection (Some models)
Drive selection is a system to switch the vehicle's drive mode. When the sport mode is selected, vehicle's response against accelerator operation is enhanced. This provides additional quick acceleration which may be needed to safely make maneuvers such as lane changes, merging onto freeways, o ...

Mazda 6 Service Manual: Immobilizer system reprogram procedure
Note When an error occurs during the reprogram procedures, except when the PCM is replaced, repeat the procedure from Step 1. If you still cannot reprogram, confirm how many keys can start the engine. Then, perform the key replacement or addition reprogram procedure according to the val ...