An illuminated Check Engine Light could indicate that one or more of the ignition coils has failed due to excessive spark plug gap. To fix this problem, the ignition coils that have failed, the spark plugs, and all coil boots should be replaced.
Car Problem Reports
Ford F-350 Super Duty Ignition Coil Failure Due to Excessive Spark Plug Gap
Ford F-350 Super Duty Problem
Engines Affected: 5.4L V8, 6.0L V8 Diesel Turbo, Gasoline