If your 2020 Subaru Impreza is showing diagnostic trouble code P0306, indicating a cylinder 6 misfire, this code requires special diagnostic consideration. The 2020 Impreza is powered by a four-cylinder boxer engine, which means there is no sixth cylinder to experience a misfire.
2020 Impreza Engine Specifications
All 2020 Subaru Impreza models use the FB20 2.0-liter horizontally-opposed four-cylinder engine, producing 152 horsepower and 145 lb-ft of torque. This naturally aspirated boxer engine features Subaru's direct injection system and includes only four cylinders in an opposing bank configuration. The cylinder numbering runs from 1-4 only.
Why P0306 Cannot Be Legitimate
Code P0306 specifically identifies cylinder 6 as the misfire source. Since the Impreza engine physically contains only cylinders 1 through 4, this code represents either a diagnostic system malfunction or data corruption rather than an actual engine condition. The ECM or scanning equipment is misidentifying the problem.
Diagnostic Investigation
Begin by confirming the code with a different scan tool, ideally Subaru's factory SSM system. Check for aftermarket devices connected to the OBD-II port that may be interfering with diagnostic communication. Inspect ECM connectors and wiring for damage or corrosion. If actual misfire symptoms exist, focus troubleshooting efforts on the four real cylinders.
Real Misfire Diagnostics
The 2020 Impreza's boxer engine can develop genuine misfires from common causes: ignition coil failure, worn spark plugs, fuel injector issues, or low compression. These conditions would generate codes P0301-P0304 rather than P0306. If your Impreza runs rough, diagnose based on symptoms and focus on cylinders 1-4.