What was found
SITTING AT GATE WITH PCA CONNECTED, STARTED TO SMELL EXTREMELY STRONG OIL ODOR. MX STARTED APU, DISCONNETED PCA, TURNED NR 2 AND SAME ODOR RETURNED IN COCKPIT NOT IN CABIN. R & R LT PACK ACM AND OPS CHECKED GOOD IAW AMM 21-51-03 AND 21-51-00. PACKS WERE OPERATED UNTIL RESIDUAL ODOR WAS ELIMINATED.