What was found
(CAN) IN CRUISE FLIGHT CREW RECEIVED PROX SYS CHAN FAULT CAUTION MESSAGE AS WELL AS (3) RED GEAR INDICATIONS, IAW AFM HAD TO PERFORM ALTERNATE EXTENSION, FLIGHT LANDED WITHOUT INCIDENT. AFTER MAINTENANCE TROUBLESHOOTING THE MDC IS POINTED TOWARDS THE PSEU ITSELF. THE PSEU WAS REPLACED AND FUNCTION TESTS WERE CARRIED OUT AND GEAR SWINGS AND THE AIRCRAFT WAS RETURNED TO SERVICE. PRESENT AC HRS:24426:01 AND CYCLES: 20077 (TC NR 20070518006)