What does code P0304 mean on a Mercedes-Benz and is it safe to drive?
P0304: Cylinder 4 Misfire Detected. Here's what it means on your Mercedes-Benz, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
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 Mercedes-Benz
- 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 Mercedes-Benz, 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 Mercedes-Benz
Mercedes M271 turbocharged four-cylinder P0304 typically indicates a failed ignition coil or worn spark plug. The M271 uses a coil-over-plug design and coil failures are not uncommon past 80k miles. On M272 V6, balance shaft gear inspection applies before coil diagnosis.
Most commonly affected models