As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTS STRANGE SMELL FROM FLIGHT DECK. REMOVED FROM SERVICE. PERFORMED OPS TEST OF ECS IAW AMM TASK 21-61-00-710-803. NO SMELL NOTED IN FD OR CABIN. PERFORMED OPS TEST OF ECS AGAIN WITH ENGINE RUNS IAW AMM TASK 21-61-00-710-802. NO SMELL NOTED DURING OPS TEST & OPS TEST GOOD. NO FURTHER DEFECTS NOTED. COULD NOT DUPLICATE SMELL. RETURNED TO SERVICE.