When your 2023 Ford Mustang displays the P0305 code, the powertrain control module has detected repeated misfires in cylinder 5. The 2023 Mustang offers the 2.3L EcoBoost four-cylinder and the 5.0L Coyote V8. P0305 is valid only on GT models equipped with the V8, as the EcoBoost has only four cylinders.
2023 Mustang Engine Identification
The 2023 model year represents the final year of the S550 generation. The EcoBoost produces 310 horsepower from its 2.3L turbocharged four-cylinder. The GT features the 5.0L Coyote V8 producing 460 horsepower standard. If you have the four-cylinder, P0305 is anomalous and represents a diagnostic error.
Cylinder 5 on the Coyote V8
The 5.0L Coyote V8 positions cylinder 5 on the driver side bank toward the rear. This engine features dual overhead camshafts, four valves per cylinder, and Ti-VCT variable valve timing. The sophisticated valvetrain requires consistent spark timing and fuel delivery for optimal performance.
Common Causes
Even on a newer 2023 model, spark plug issues can occur if the vehicle has been tracked or driven hard. Ignition coil failure, though less common on newer vehicles, can still happen. Manufacturing defects or loose connections at the coil can cause intermittent misfires. Fuel system issues including injector performance should be considered.
Diagnostic Approach
Verify this is a GT with the V8 engine. Check for any Technical Service Bulletins specific to 2023 Mustang misfire issues. Access cylinder 5's spark plug on the driver side rear and inspect. Test the ignition coil. Review freeze frame data to understand operating conditions when the misfire occurred.