The P0302 code in your 2018 Toyota Avalon indicates a misfire in cylinder 2, and the vibration you're feeling is the engine running unevenly due to incomplete combustion in that cylinder. Your Avalon uses the 3.5L V6 (2GR-FKS) with both port and direct injection—a sophisticated engine that requires all six cylinders firing properly for smooth operation.
Why Misfires Cause Vibration
When a cylinder doesn't fire properly, it doesn't produce power during its combustion stroke but still creates resistance during other strokes. This creates an imbalance that you feel as vibration. A V6 with one cylinder misfiring is noticeably rougher than when all cylinders fire properly.
Cylinder 2 Specific Causes
Failed ignition coil for cylinder 2. Worn or fouled spark plug. Fuel injector problem (port or direct injector). Low compression from valve issues, head gasket, or rings. Vacuum leak near cylinder 2 intake port. Carbon buildup on intake valves affecting cylinder 2.
System-Wide Possibilities
While P0302 points to cylinder 2, some issues affect single cylinders randomly. Fuel quality issues may affect the first cylinder to show weakness. Check for additional codes that might indicate broader problems.
Diagnostic Approach
Check misfire counters for all cylinders—if only cylinder 2 is affected, focus there. Swap the cylinder 2 ignition coil with another cylinder and see if the misfire follows. Check spark plug condition. Test fuel injector operation. Perform compression test if ignition and fuel check out.