2021 Mazda P0300: What It Means & Is It Safe to Drive?
P0300 on the 2021 Mazda: Random/Multiple Cylinder Misfire Detected. Here's what it means, what usually causes it, what repairs typically cost, and whether it's safe to keep driving.
What this code means
The PCM has detected misfires across multiple cylinders. This can cause damage to the catalytic converter if driven for long.
Common causes on the 2021 Mazda
- Worn spark plugs or ignition coils
- Clogged or bad fuel injectors
- Low compression
- Vacuum leak, bad MAF, or fuel delivery issue
Symptoms
- Check Engine Light (often flashing under load)
- Rough idle, shaking, loss of power
- Possible smell of unburned fuel
Typical fixes
- Replace spark plugs and coils as needed
- Clean or replace fuel injectors
- Fix vacuum/fuel issues
- Compression test if no obvious cause
Repair cost range
For a 2021 Mazda, repairs for P0300 typically fall between $150 and $1200, depending on the root cause and labor rates in your area.
Known issues on Mazda
Mazda P0300 on SkyActiv-G 2.5L engines is relatively uncommon. When it occurs after 100k miles, direct injection intake valve carbon buildup is the most likely cause—the Mazda SkyActiv uses DI-only fueling (no port injection), which accelerates carbon buildup. On Mazdaspeed3 2.3T, P0300 during hard acceleration indicates a boost leak. RX-8 13B Wankel engine P0300 is a completely different failure mode—Wankel apex seal wear causes systematic misfires and the 13B is unusually sensitive to oil viscosity and cold-start technique.
Most commonly affected models