A P0304 diagnostic code on your 2017 Toyota Corolla indicates the engine control module has detected repeated misfires in cylinder 4. The 11th generation Corolla uses the proven 1.8L four-cylinder engine.
1.8L Engine Layout
The 2017 Corolla uses the 2ZR-FAE 1.8L four-cylinder producing 132 horsepower with Valvematic variable valve timing. This port-injected engine is known for reliability. Cylinder 4 is the rearmost.
Common Causes
- Ignition Coil Failure: Age-related degradation
- Spark Plug Wear: May be at service interval
- Fuel Injector Issues: Port injection deposits
- Vacuum Leaks: Aged gaskets and hoses
- PCV System: Positive crankcase ventilation issues
Diagnostic Approach
Use a Toyota-compatible scanner for diagnostics. The port injection system is simple and reliable. Monitor misfire counts. Test ignition components.
Repair Solutions
Replace aging ignition coils with Denso parts. Install new spark plugs. Clean fuel injectors. Repair vacuum leaks and PCV system issues.