When your 2024 Subaru Crosstrek displays the P0304 code, the engine control module has detected recurring misfires in cylinder 4. The adventure-ready compact crossover's boxer engine requires understanding of Subaru's unique horizontally-opposed design for effective diagnosis.
Understanding P0304 in the 2024 Crosstrek
The 2024 Crosstrek offers the 2.0L FB20 boxer four-cylinder in base models or the 2.5L FB25 in Premium and higher trims. Both horizontally-opposed configurations position cylinder 4 at the rear of the left (driver's) bank. Subaru's engine management precisely identifies the misfiring cylinder through crankshaft velocity analysis.
Boxer Engine Misfire Causes
Subaru's flat-four boxer places cylinders horizontally opposite each other. Spark plugs install sideways rather than vertically. Standard ignition causes—coil degradation and plug wear—apply with the boxer's unique service geometry. The Crosstrek's adventure-oriented use may expose ignition components to environmental stress.
Diagnostic Methodology
Identify your engine size—2.0L or 2.5L. Retrieve all codes and freeze frame data. Locate cylinder 4 on the left bank rear position. Access requires working around the inner fender area. Test ignition coil output and spark plug condition. Verify fuel injector operation.
Repair Solutions
Install Subaru-specified spark plugs for your engine type. Clean spark plug wells before removal. Replace degraded ignition coils. Address fuel system concerns. Inspect for environmental damage if the vehicle sees frequent off-road or adventure use.