When your 2021 Ford Bronco displays the P0305 code, the powertrain control module has detected repeated misfires in cylinder 5. The 2021 Bronco (first model year of the revival) offers two engine options: the 2.3L EcoBoost four-cylinder and the 2.7L EcoBoost V6. P0305 is valid only on Broncos equipped with the V6, as the four-cylinder has only cylinders 1-4.
Identifying Your Bronco's Engine
The 2.3L EcoBoost I-4 produces 270-300 horsepower depending on fuel grade. The 2.7L EcoBoost V6 produces 310-330 horsepower. Check your window sticker, door jamb label, or Bronco's infotainment system to confirm which engine is installed. If you have the 2.3L four-cylinder, P0305 is anomalous.
Cylinder 5 Location on the 2.7L V6
Ford's 2.7L EcoBoost V6 uses a 60-degree bank angle with cylinder 5 positioned on the passenger side bank toward the rear. This twin-turbocharged engine requires precise ignition timing and robust spark plugs to handle the increased cylinder pressures.
Common Causes in the 2.7L EcoBoost
Spark plug issues can develop even on newer engines, particularly with turbocharged powertrains that create higher cylinder pressures. Ignition coil failure at cylinder 5 is possible. Direct injection engines like the 2.7L EcoBoost can develop carbon buildup on intake valves over time. Boost leaks or wastegate issues can affect cylinder performance inconsistently.
Diagnostic Steps
Confirm you have the V6 engine. Access cylinder 5's spark plug on the passenger side rear and inspect. Check the ignition coil for proper function. Look for boost leaks that could affect air-fuel ratios. As a first-year model, check for TSBs that may address known issues.