As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNABLE TO OBTAIN SELCAL CHECK ON HF 1 OR 2. LARGE AMOUNT OF ENGINE NOISE FEEDBACK COMING THROUGH RADIOS MAKING COMMUNICATIONS UNINTELLIGIBLE. GROUNDED - YES. PERFORMED SYSTEM TEST OF HF1 AND HF2. OPS CHECKS PASSED. REF B737-9 AMM 23-11-00-730-801.