What was found
AIRCRAFT WAS GROUNDED: FLIGHT RETURNED TO ONT ON ACCOUNT OF LEFT ENGINE OIL BYPASS LIGHT ILLUMINATED. AN EMERGENCY WAS DECLARED. MAINTENANCE FOUND COKE/CARBON PARTICLES ON THE SCAVENGE FILTER. REMOVED AND REPLACED L/H ENGINE SCAVENGE OIL FILTER IAW AMM 79-21-06, LEAK CHECK GOOD. REMOVED AND REPLACED L/H ENGINE SCAVENGE OIL FILTER TRANSMITTER IAW AMM 79-21-07, LEAK CHECK GOOD. ACCOMPLISHED MCD AND SCAVENGE SCREENS INSPECTION IAW AMM 79-00-00, LEAK CHECK GOOD.***SUPPLEMENTAL INFORMATION: MAINTENANCE REMOVED AND REPLCED LEFT ENGINE IAW JOB CARD 71-94-01. ALL CHECKS GOOD.*** ***SUPPLEMENTAL WILL BE FILED UPON ADDITIONAL ENGINE INFORMATION***(OPEN)