2009 E350 (211.056) with 89,000 miles; presents with two fault codes:

1337 - Alternator Serial interface

1897 - no description given (other than MIL on and stored and current event)


Clearing the codes results in immediate recurrence of the codes once the engine is restarted.

Vehicle is asymptomatic and performs flawlessly; no red colored battery icon or charging system warnings have appeared in the instrument cluster.

Vehicle has a one year old Mercedes battery which displays 13.1 V with the engine off. With the engine at idle and no ancillary systems engaged a reading of 14.2 V is displayed.

Any recommendations as to the next diagnostic step? Might this indicate a voltage regulator issue?

Your alternator voltage output is digitally controlled by the ECU. Code 1337 means the ECU is no longer able to communicate with the alternator. As a failsafe, thd alternator's voltage regulator is smart enough to keep working even if it lost communication. Inspect the wiring to the alternator and the plastic plug on the back of the alternator. If that all seems fine, replace the voltage regulator.

__________________
CENSORED due to not family friendly words