My 2002 Liberty has only 26,000 miles on it...has given us no problems in the past. While driving it 6 wks. ago, the check engine light appeared, my husband disconnected the battery which then made the light disappear only to have it come back on in the next few days...I have replaced the gas cap twice(first from Autozone, then factory gass cap). The mechanic performed a diagnostic check & reassured me he could find nothing else wrong, my neighbor insists that because I still have the original battery, it may be causing the engine light to come on due to it being old?