What does code P0304 mean on a Mazda and is it safe to drive?
P0304: Cylinder 4 Misfire Detected. Here's what it means on your Mazda, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
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What this code means
Misfire confirmed on cylinder 4. On 4-cylinder engines, this is the last cylinder—check coil and plug first, then injector, then compression.
Common causes for your Mazda
- Worn spark plug on cylinder 4
- Failed ignition coil on cylinder 4
- Faulty or clogged fuel injector
- Low compression or valve issue
Symptoms
- Check Engine Light
- Rough idle and shaking
- Poor acceleration or power loss
Typical fixes
- Replace spark plug and COP coil on cylinder 4
- Clean or replace fuel injector
- Compression and leak-down test if basic parts check out
Repair cost range
For a Mazda, repairs for P0304 often fall between $150 and $900, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Mazda
SKYACTIV-G P0304 on cylinder 4 is typically injector fouling. If multiple cylinder misfires appear at different times, the injector cleaning is needed for all four cylinders simultaneously given the direct injection design.
Most commonly affected models
Mazda3 SKYACTIV-G 2012–2018CX-5 2013–2018Mazda6 2014–2018