What was found
DURING TAXI OUT, OIL PRESSURE INDICATION IS ERRATIC, FLUCTUATING BETWEEN 0 TO NORMAL. ALL OTHER ENGINE INDICATIONS NORMAL. AC RETURNED TO THE GATE (BTB) AND MTX GROUNDED AC.REMOVED AND REPLACED THE L EICAS COMPUTER IAW AMM 31-41-02 PERFORMED CROSSLOAD OF SOFTWARE FROM R COMPUTER IAW AMM 31-41-02. OPS CHECK GOOD AT THIS TIME.. PERFORMED DRY MOTOR OF ENGINES IAW AMM 71-00-00. NO DEFECTS NOTED ON OIL PRESSURE INDICATION. A/C RELEASE NO ETOPS RETURNED AC TO SERVICE.