I had an engine light go on after gas cap warning lit up (never fill up w engine running) and since then the mds system keep going into less cyclinders very quickly....when i put a code reader on it stated that there was a problem with an evap sensor....since that time battery went dead, the engine lights all went out and the evap sensor error is gone, but the problem w the mds still exists. Brought truck to dealer they said no problem is found...only that the battery was not keeping a charge...battery replaced still w mds problem....any suggestions??? thanks in advance

 

Check the oxygen sensor,
FF