Carbon build-up, coolant pump and 48V system faults
M256Rough cold running, a coolant loss, or an electrical fault tied to the starter-generator.
The known cluster on this engine is carbon on the intake valves, coolant pump failure, complexity around the 48-volt integrated starter-generator, and timing chain wear. The ISG is not a conventional starter motor and is not priced like one.
Parts this needs
Checked against motorreviewer.com

