Mah_c180 Posted June 7, 2014 Report Share Posted June 7, 2014 2F99 CDKTUM - Ambient Temperature and 2EF5 CDKETS - Thermostat characteristic diagram cooling. Could this mean, why I'm having a loss of oil? I know that the thermostat needs to be changed, but what's the first code? Link to comment Share on other sites More sharing options...