As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
#1 HANDLE DOES NOT ILLUMINATE DURING FIRE TEST. GROUNDED - YES. REPLACED FIRE DETECTION HARNESS MW0316 LOOP PER B737-800 AMM 26-11-02, INTERMITTENT FAULT. WHILE CLOSING T/R AND DOING A BITE TEST, LOOP B LIGHT FLICKERING. REF AMM 26-10-01/401 REMOVED AND REPLACED FIRE DETECTION UNIT, PERFORMED OPS AND BITE TEST SEVERAL TIMES AND PASSED BOTH #1,2 ENGINE FIRE LOOP-B WORKS NORMAL.