As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ANTI-ICE WING CAUTION SYSTEM CANNOT PROVIDE ICE PROTECTION TO TWO OR MORE ZONE PAIRS O N THE WING OR LOSS OF COMMUNICATION FROM THE WIPCU TO DCA. TEST PASSED MULTIPLE TIMES. PLUG, UPON INSPECTION OF HEATING MATS FOUND CONNECTOR BEHIND REINSTALLED ACCESS PANELS REF 30-11-05 PANEL 525AB (HEATER 21) DISCONNECTED. CONNECTED HEATER MAT PLUG REF AMM 30-11-05. PERFORMED WING ICE PROTECTION SYSTEM TEST REF