What does code P0300 mean on a Hyundai and is it safe to drive?
P0300: Random/Multiple Cylinder Misfire Detected. Here's what it means on your Hyundai, what usually causes it, what repairs typically cost, and how safe it is 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 for your Hyundai
- 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 Hyundai, repairs for P0300 often fall between $150 and $1200, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Hyundai
Hyundai P0300 on Theta II 2.4L GDI engines is a serious warning—the Theta II rod bearing failures (subject to multiple recalls) can cause cylinder-specific misfires before bearing knock becomes audible. Check your VIN for open Hyundai recalls before assuming a routine ignition cause. Carbon buildup on intake valves (a GDI-specific issue) also causes intermittent P0300 at cold startup on these engines. On Tucson 2.0L Nu GDI, spark plug replacement at the recommended 30k interval is critical—extended intervals lead to electrode erosion and misfire.
Most commonly affected models