One problem related to check engine light on has been reported for the 1999 Mercedes Benz E320. The most recently reported issues are listed below.
: the contact stated the check engine light illuminated while driving. The vehicle was taken to the dealer where it was determined by diagnostic testing the air mass sensor needed to be replaced. The contact stated also owns an ml320 which had the same failure July 2006. If the air mass sensor is not replaced, further damage can result to the engine.