What was found
INTERMITTENT COM 1 TRANSMIT PROBLEM ON CLIMB OUT. ON COM 2 DISPLAY ON L PFD, R PFD/COM. WORKED NORMALLY UNTIL LEVEL AT CRUISE. THEN UNABLE TO TR/RX ON COM 1 ON EITHER SIDE. COM 2 FUNCTIONED NORMALLY, BUT THEN STUCK ON 121.8 (LAST FREQ IN ACTIVE). ACTIVE (WINDOW) AND UNABLE TO SWAP FREQUENCY OR CHANGE STBY MORE THAN 1 MBZ 5 MINUTES LATER L PFD COM1/COM2 BUTTON CONTROLLED COM1/COM 2SELECTION ON R PFD. MINUTES LATER L PFD NAV FUNCTIONS FAILED INCLUDING NAV1,NAV2 WORKED BUT WAS UNCHANGEABLE IN FREQUENCY FIELDS. LANDING WHITE ADVISORY CAS "AVIONICS DATA BUSS FAIL". REMOVED AND REPLACED LEFT PFD WITH A REPAIRED UNIT IAW EA500 AMM 31-10-16. PERFORMED OPERATIONAL CHECKS OF LEFT PFD IAW EA500 AMM 31-00-00, NO DEF