As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE TOILET CAUTION MESSAGE ON ARRIVAL. SUSPECT APU IS AT FAULT BECAUSE IT APPEARED WHEN I TURNED IT ON AND DISAPPEARED WHEN I TURNED IT OFF. FLIGHT 3844 CLOSED TROUBLE SHOT SMOKE IN CABIN IAW FIM. FOUND APU TO BE OVER SERVICED. PROPERLY SERVICED APU IAW AMM. PERFORMED OPS CHECK OF BOTH PACKS IAW AMM, RAN PACKS INDIVIDUALLY OFF OF THE APU AND ENGINES, NO SMOKE PRODUCED AND OIL SMELL DISSIPATED. PLEASE REFERENCE AML 322127 AND PLEASE REFERENCE AML 322128 FOR R&R OF COALESCER BAGS.