A steady check engine light with code P0302 on your 2018 Hyundai Elantra indicates a misfire specifically in cylinder 2. Unlike a flashing light that signals severe misfires, a steady light means the misfire is detected but not severe enough to immediately damage the catalytic converter.
Understanding P0302
Code P0302 indicates the engine computer has detected misfire in cylinder 2 based on crankshaft position sensor data. The computer notices variations in crankshaft rotation speed indicating that cylinder 2 isn't producing proper power during its combustion event.
Common Causes on the Elantra
Cylinder 2 misfires on the 2.0L engine commonly result from worn or fouled spark plug in cylinder 2, failed ignition coil on cylinder 2, fuel injector clogging or failure, vacuum leak near cylinder 2, and low compression in cylinder 2 from mechanical issues. Single-cylinder misfires usually point to cylinder-specific components.
Diagnostic Approach
Start with the simplest possibilities. Swap the cylinder 2 ignition coil with another cylinder - if the misfire code follows to the new cylinder, the coil is bad. Inspect the spark plug on cylinder 2 for wear, fouling, or damage. Check for vacuum leaks around the intake near cylinder 2. Test fuel injector operation.
Compression and Mechanical Issues
If ignition and fuel components check out, perform a compression test on cylinder 2 and compare to other cylinders. Low compression indicates valve, head gasket, or piston ring issues. Significant compression difference between cylinders points to mechanical problems requiring more extensive repair.
Repair and Verification
Replace the faulty component identified through diagnosis. Clear the code and test drive. Monitor for code return. If the misfire was caused by a weak coil or worn plug, the repair is straightforward. Mechanical issues require more extensive work.