If the engine fails to start, it may be flooded (excessive fuel in the engine).
Follow this procedure:
1. If the engine does not start within five seconds on the first try, wait ten seconds and try again.
2. Make sure the parking brake is on.
3. Depress the accelerator all the way and hold it there.
4. Depress the clutch pedal (Manual transaxle) or the brake pedal (Automatic transaxle), then press the push button start. If the engine starts, release the accelerator immediately because the engine will suddenly rev up.
5. If the engine fails to start, crank it without depressing the accelerator.
If the engine still does not start using the previous procedure, have your vehicle inspected by an Authorized Mazda Dealer.
Mazda 6 Owners Manual: Woofer inspection
1. Inspect for continuity between the audio amplifier connector terminals and
woofer connector terminals using an ohmmeter.
If not as specified, replace the related wiring harnesses.
2. Verify that there is battery positive voltage at the woofer connector
terminal A (4SD) or C (5HB) u ...
Mazda 6 Owners 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
...