On newer systems some deviation should be permitted (via tech documents and dealer technical support documents). An ICM (Instrument cluster module) update should be performed. On top of that, a coolant system check should be performed (leak test using proper equipment) and a thermostat performance can be checked via SDS (MB systems diagnosis). If the check passes system specifications a coolant pump diagnosis via ME actuations can be performed where it checks for proper coolant pump actuator arm operation. If it fails the coolant pump actuation it should receive a new water pump, test drive for proper operation and if temperature still rises quickly a thermostat should be replaced. Any reputable tech would agree that due to the variable ball-valve thermostat should be replaced as well. If you have a check engine light for thermostat it should receive a new thermostat, however, with proper knowledge to how the as-needed coolant and oil supply system in the m270 DIH is designed if the new water pump does not fix the issue a new thermostat will (simply how the system operates and how they function together).