Mazda 6 Service Manual: No.5 engine stalls-after start/at idle

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

No.6 cranks normally but will not start

Other materials:

Mazda 6 Service Manual: Ignition switch inspection
1. Disconnect the negative battery cable. 2. Remove the column cover. (See COLUMN COVER REMOVAL/INSTALLATION) 3. Disconnect the ignition switch connectors. 4. Inspect for continuity between the ignition switch terminals using an ohmmeter. If not as specified, replace the ignition switch. ...

Mazda 6 Service Manual: Troubleshooting procedure
Basic flow of troubleshooting DTC troubleshooting flow (on-board diagnostic) Diagnostic trouble codes (DTCs) are important hints for repairing malfunctions that are difficult to simulate. Perform the specific DTC diagnostic inspection to quickly and accurately diagnose the malfunction. The ...