What was found
FLT 1203 EWR-SDQ RETURNED TO EWR. ELECTRICAL ODOR LATER DETERMINED TO BE OILY CABIN ODOR ISOLATED TO PACK 1 WHILE IN OPERATION (PACK-SINGLE-N703 AND UP), SPEEDBRAKES OK. R & R PACK 1 OZONE FILTER, IAW AMM 21-51-41. OPERATIONS CHECK GOOD, NO SMELL ODOR NOTED. COMPLIED WITH INFOMATIION NOTICE 2017-T015F SECTION A CLEARS MDDR MX-4, UPDATED MCC NOTIFED.