The snap on scanners can reset those,I think it was under the special functions section.That is a seperate unit from main computer,Turns one by pre determined time/miliege.Supposed to have emission system checked for proper working.(eg)egr valve, cat conv,vacuum hoses,etc.I can look on mitchell wednesday for procedure.Some needed the module replaced,some had a 9v battery to replace,some even had a button you just push.unit is behind the instrument cluster/dash.Light has NO indication of an actuall problem.