What was found
WHILE PERFORMING CSS AT FL370, APU FAULT LIGHT ILLUMINATED AFTER LIGHT OFF. PERFORMED QRH PROCEDURE, EGT REACHED ABOUT 1000 DEGREES BEFORE THE FAULT LIGHT CAME ON. SAT WAS -53. SECOND ATTEMPT AT FL320 FAILED WITH THE SAME INDICATIONS. NO TIME FOR A THIRD ATTEMPT. APU STARTED NORMALLY AFTER LANDING. GROUNDED - YES. PERFORMED APU OPERATIONAL TEST PER B737-800 AMM 49-11-00-710-801. NO FAULTS NOTED. APU BITE CK UNDER FAULT HISTORY SHOWS MSG 49-31016 HIGH EGT AUTO SHUTDOWN FOR THE TWO INFLIGHT ATTEMPTS. ENGINEERING REQUEST - REMOVED AND REPLACED APU LUBE MODULE REF AMM 49-91-11. OPS AND LEAK CHECK GOOD.