A P0302 code on your 2017 Honda Fit indicates a misfire in cylinder 2, and when felt as vibration at idle, the misfire is occurring consistently enough to upset the engine's balance. The Fit's 1.5-liter four-cylinder engine is relatively smooth when running properly, so a single-cylinder misfire becomes quite noticeable.
Why Cylinder 2 Misfires Cause Vibration
In a four-cylinder engine, each cylinder fires in sequence to create smooth, continuous power. When cylinder 2 fails to produce its power pulse, the engine becomes unbalanced—essentially running on three cylinders momentarily. This creates the rhythmic vibration you feel at idle, where there's no vehicle motion to mask the uneven running.
Common Causes in the Fit 1.5L
The direct-injection 1.5-liter engine in the 2017 Fit has specific characteristics that affect misfire diagnosis. Spark plug condition is critical—the high compression ratio demands strong spark. Ignition coils can fail, particularly in high-mileage or heavily-driven vehicles. The direct fuel injectors themselves can become clogged or fail. Less commonly, mechanical issues like low compression or valve problems cause persistent misfires.
Diagnostic Process
Start with the ignition system. Remove the cylinder 2 spark plug and inspect for wear, carbon buildup, or damage. Check the gap—it should be 0.039-0.043 inches for this engine. Swap the cylinder 2 ignition coil with an adjacent cylinder (cylinder 1 or 3), clear the code, and idle the engine. If the misfire moves to the new cylinder, the coil is faulty. If it stays at cylinder 2, continue diagnosis.
Fuel Injector Testing
Direct fuel injectors can be tested using a stethoscope—each should click at the same rhythm. You can also use a scanner to perform an injector balance test if your tool supports it. A significantly weak or non-functioning injector will cause consistent misfire. Injector cleaning services are available, though replacement is sometimes more reliable for failed injectors.
Repair Costs
Spark plug replacement for all four cylinders (recommended even if only one is fouled) costs $100-$200 including labor. Individual ignition coil replacement runs $100-$180. A single direct fuel injector costs $150-$250 for the part, with labor adding $100-$200 due to fuel system access requirements. If compression is the issue, more extensive repairs may be necessary, though this is rare on low-mileage Fits.