There are several things.
Low engine oil level, low oil pressure, sludge in engine oil passages from poor oil change history.
The poor oil change history effects can cause the solenoid controlling valve timing to stick or the hub on camshaft that is the servo changing valve timing to stick.
The solenoids have had some instances of getting debris in them from things that can pass through oiling system on occasion that sticks the solenoid in open position.
The last can happen with regular oil and filter service.
The code sets for the valve timing not going to the regulated position desired by the engine control module.
The solenoid controlling the exhaust valve timing is placed over the exhaust camshaft which is the rear cam as engine is situated in vehicle. The solenoids have been cleaned with some success and there may be a strainer in the supply hole to the solenoid that needs to be cleaned or replaced. The strainer may be integral with the solenoid also.