What was found
FLT 278 - MEX-CJS - AIRCRAFT RETURNED TO PLATFORM AS A CONSEQUENCE OF DURNIG PUSH-BACK APU SHUTOFF AND APU FIRE, OVERSPEED, AND TAKEOFF ALARMS WERE ACTIVATED. AT PLATFORM, ALARM SYSTEM (CAWS) WAS RESET BUT FAIL CONTINUED. IT WAS REPLACED AND TESTED IAW MM 31-51-01, ALL CORRECT. DURING OVERNIGHT SERVICE, ALARMS SYSTEM WAS TESTED IN CAWS COMPUTER IAW MM 31-50-00, 31-51-01, ALL CORRECT. ADDITIONALLY FIRE DETECTION SYSTEM WAS TESTED IAW MM 26-00-00, ALL CORRECT. APU WAS OPERATING CORRECT IAW MM 49-00-00. (M)