# JASC 4970: APU Indicating System - Type: JASC system/component code (FAA) - ATA chapter: 49 Airborne Auxiliary Power - Title in the code table: APU INDICATING SYSTEM - Service difficulty reports: 272 - FAA code table: https://www.faa.gov/sites/faa.gov/files/JASC_Code.pdf#page=44 - Page: https://openairdocs.org/jasc/4970 ## What it covers For general reports of APU operation indicating including the temperature indicator, tachometer generator or indicator (engine speed). Includes the instrument and associated warning system which sense, transmits, and indicates APU engine speed and temperatures to the flight crew. ## Service difficulty reports (272, newest 50) - [SDR SWAA2026101474131](https://openairdocs.org/sdr/SWAA2026101474131), Oct 10, 2026: Boeing 7378. APU. FAULT MESSAGE. APU FAULT LIGHT ILLUMINATED. APU AUTO SHUTDOWN, TURNED APU SWITCH OFF ACCORDING TO QRH. FAULT LIGHT EXTINGUISHED AFTER 3 (N8841L) - [SDR UIEA2025120501334](https://openairdocs.org/sdr/UIEA2025120501334), Dec 5, 2025: Boeing 74787UF. WARNING MESSAGE. ILLUMINATED. EICAS APU INDICATION IN FLIGHT. APU DUCT LEAK STATUS MSG. QRH COMPLIED WITH (APU FIRE HANDLE PULLED)(

OPERATED APU FOR (N856GT) - [SDR ABXA20251019274](https://openairdocs.org/sdr/ABXA20251019274), Oct 19, 2025: Boeing 76736N. BATTERY. FAULTED. DURING TAXI ,APU BATTERY, NO STBY STATUS MESSAGE DISPLAYED. ADVISED BY MTC TO RETURN TO PARKING (BTB). MTX GROUNDED ACFT (N1013A) - [SDR HALA20250728234](https://openairdocs.org/sdr/HALA20250728234), Jul 25, 2025: Airbus A330243. SENSOR. FAILED. ETOPS - APU AUTO SHUTDOWN. PERFORMED WIRING CHECKS OF SPEED SENSORS 59KV56 AND 59KV57 PER TSM 49-62-00-810-805-A. 59KV26 (N396HA) - [SDR ASAA2023042342988](https://openairdocs.org/sdr/ASAA2023042342988), Apr 23, 2023: Boeing 737890. DATA UNIT. FAULTY. DURING APU TROUBLESHOOTING FOUND MESSAGE 49-72103 "DATA MEMORY MODULE CIRCUIT FAILURE". SUSPECT APU WIRING HARNESS. GROU (N570AS) - [SDR ASAA2023022642081](https://openairdocs.org/sdr/ASAA2023022642081), Feb 26, 2023: Boeing 7379. MODULE. FAULTY. AIRCRAFT IS REPORTING REPETITIVE APU DMM CIRCUIT FAULT, 49-72105. GROUNDED - YES. PERFORMED TROUBLESHOOTING IAW B737-9 I (N943AK) - [SDR ASAA2022090539823](https://openairdocs.org/sdr/ASAA2022090539823), Sep 5, 2022: Boeing 737890. MEMORY DEVICE. FAULTED. APU BITE SHOWS FAULT CODE 49-72101 LAST 18 STARTS. GROUNDED - YES. REMOVED AND REPLACED DATA MEMORY MODULE IAW B737-800 (N538AS) - [SDR SWIA202266220](https://openairdocs.org/sdr/SWIA202266220), Jul 25, 2022: Cndair CL6002D24. APU. OUT OF ADJUST. D: APU DOOR OPEN IN FLIGHT. WOULD NOT CLOSE. / C: DEFERRED APU DOOR OPEN PER MEL 49-14-1B. C/W MX ACTION. PLACARD INSTAL (N897SK) - [SDR ASAA2022050438232](https://openairdocs.org/sdr/ASAA2022050438232), May 4, 2022: Boeing 737890. MODULE. FAULT MESSAGE. THE APU FAILED TO START ON TAXI IN . FAULT LIGHT ILLUMINATED. GROUNDED - YES. REMOVED & REPLACED DATA MEMORY MODULE REF (N513AS) - [SDR ASAA2021092536095](https://openairdocs.org/sdr/ASAA2021092536095), Sep 25, 2021: Boeing 737890. WARNING LIGHT. ILLUMINATED. BLUE MAINT LIGHT ILLUMINATED AFTER STARTING APU ON THE GROUND AFTER LANDING. GROUNDED - YES. APU BITE CHECK SHOWS MAINT (N597AS) - [SDR UIEA2021091102005](https://openairdocs.org/sdr/UIEA2021091102005), Sep 9, 2021: Boeing 7673S1. FAULT MESSAGE. FALSE ACTIVATION. APU FAULT MAX EGT 778 RPM 39(

PERFORMED APU ECU BITE CHECK IAW 49-61-05. NO FAULTS PRESENT. PERFORMED OPERATIONAL CHEC (N640GT) - [SDR ASAA2021090535866](https://openairdocs.org/sdr/ASAA2021090535866), Sep 5, 2021: Boeing 737890. THERMOCOUPLE. FAULTED. APU FAULT X2 APU NOT STARTING. GROUNDED - YES. BITE CHECK C/W. FOUND FAULT MSG 49-491012 TWICE, AND 49-71147 & 49-71148 (N530AS) - [SDR UIEA2020122002596](https://openairdocs.org/sdr/UIEA2020122002596), Dec 20, 2020: Boeing 767306. WARNING LIGHT. FALSE ACTIVATION. ITEM 3-APU FAULT ON LANDING/TAXI IN. RE-START OK. PERFORMED BITE CHECK OF THE APU ECU, IAW 49-61-05, NO FAULTS FOUND. OK (N1409A) - [SDR UIEA2020071501555](https://openairdocs.org/sdr/UIEA2020071501555), Jul 14, 2020: Boeing 767306. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT MESSAGE ON FIRST START ATTEMPT AFTER LANDING, SECOND ATTEMPT STARTED NORMALLY. PERFORMED BITE CHECK OF APU ECU (N1409A) - [SDR UIEA2020071401527](https://openairdocs.org/sdr/UIEA2020071401527), Jul 10, 2020: Boeing 76731K. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT AFTER LANDING DURING 1ST START ATTEMPT. RE-START NOT ATTEMPTED. PERFORMED FIM PROCEDURE 49-11 F/T 958, NO FAUL (N1373A) - [SDR ASAA2020070632869](https://openairdocs.org/sdr/ASAA2020070632869), Jul 4, 2020: Boeing 737890. SENSOR. SHORTED. APU FAILURE TO START. FAULT MESSAGE INLET TEMP SENSOR SHOWS SHORT. GROUNDED - YES. REMOVED AND REPLACED APU INLET TEMP S (N519AS) - [SDR UIEA2020060801217](https://openairdocs.org/sdr/UIEA2020060801217), Jun 5, 2020: Boeing 76731K. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT EICAS MESSAGE WHEN ATTEMPTED START ON TAXI IN. PERFORMED BITE CHECK ON APU ECU, NO FAULTS FOUND. APU STARTED F (N1487A) - [SDR UIEA2020060101185](https://openairdocs.org/sdr/UIEA2020060101185), May 28, 2020: Boeing 767306. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT MSG. RECYCLED APU AND PERFORMED BITE TEST. NO FAULTS NOTED AT THIS TIME. EICAS SHOWS NO MESSAGES. APU AND OPER (N1409A) - [SDR UIEA2020052901150](https://openairdocs.org/sdr/UIEA2020052901150), May 28, 2020: Boeing 767375. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT DURING APU START. PERFORMED APU BITE TEST IAW FIM 49-11 FT 958, FOUND FAULT 34, CLEARED. PERFORMED OPERATIONAL (N649GT) - [SDR ASAA2020051732740](https://openairdocs.org/sdr/ASAA2020051732740), May 17, 2020: Boeing 737990ER. WARNING SYSTEM. FALSE ACTIVATION. CSS FAILED FL 400 (3 ATTEMPTS), FAULT LIGHT ILLUMINATED. GROUNDED - YES. FOUND FAULT 49-31016 OVERTEMP SHUTDOWN. IAW FIM (N487AS) - [SDR UIEA2020050400940](https://openairdocs.org/sdr/UIEA2020050400940), May 3, 2020: Boeing 767324. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT ON LANDING.(

FOLLOWED FAULT TREE FIM 49-11 FT 987 - FOR APU ECU BITE - NO DATA DISPLAYED.

APU OPERATIN (N645GT) - [SDR UIEA2020042900914](https://openairdocs.org/sdr/UIEA2020042900914), Apr 28, 2020: Boeing 767306. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT (

BEGAN APU BITE PROCEDURE. PERFORMED TWO SUCCESSFUL STARTS DURING OPS CHECK IAW AMM 49-11-00. OPS CHEC (N1427A) - [SDR UIEA2020042800882](https://openairdocs.org/sdr/UIEA2020042800882), Apr 28, 2020: Boeing 76731K. WARNING SYSTEM. FALSE ACTIVATION. STARTED APU AFTER LANDING. IT WAS RUNNING WHEN WE BLOCKED IN. WHEN WE SHUTDOWN ENGINES APU FAULT CAME ON AND APU SHUTDOW (N1373A) - [SDR UIEA2020042800880](https://openairdocs.org/sdr/UIEA2020042800880), Apr 27, 2020: Boeing 76731K. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT EICAS.(

PERFORMED BITE ON APU MODULE AND FOUND NO FAULTS ON LRU OR PREVIOUS FAULT HISTORY IAW B767 AMM 49-61 (N1373A) - [SDR UIEA2020042700842](https://openairdocs.org/sdr/UIEA2020042700842), Apr 26, 2020: Boeing 767328. WARNING SYSTEM. FALSE ACTIVATION. APU BLEED VALVE MESSAGE DISPLAYED.(

PERFORMED PNEUMATIC SYSTEM TEST IAW AMM 49-11-00. SYSTEM TEST OK.

) (N1499A) - [SDR UIEA2020042800837](https://openairdocs.org/sdr/UIEA2020042800837), Apr 25, 2020: Boeing 767324. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT ON LANDING.(

PERFORMED APU BITE PER FIM 49-11 FT 987, NO FAULTS NOTED AT THIS TIME. OPS CHECK GOOD PER B767 (N645GT) - [SDR UIEA2020041600756](https://openairdocs.org/sdr/UIEA2020041600756), Apr 16, 2020: Boeing 76731K. UNKNOWN. MALFUNCTIONED. APU FAULT ON ARRIVAL(

PERFORM APU BITE TEST REF AMM 49-61-05-742-027. NO FAULTS NOTED AT THIS TIME.

) (N1373A) - [SDR UIEA2020032300534](https://openairdocs.org/sdr/UIEA2020032300534), Mar 23, 2020: Boeing 76731K. UNKNOWN. MALFUNCTIONED. APU FAULT EICAS MSG, 2ND ATTEMPT UNSUCCESSFUL, APU FAULT ON THE 2ND ATTEMPT.(

TRANSFERRED TO MDDR 126159, CAT C, PER D (N1373A) - [SDR UIEA2020032300533](https://openairdocs.org/sdr/UIEA2020032300533), Mar 23, 2020: Boeing 76731K. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT(

PERFORMED APU ECU BITE CHECK IAW B767 FIM 49-11 FT 958, SYSTEM FAULTED PT SENSOR MINI FLAG 14. RESET, CLEAR (N1373A) - [SDR UIEA2020032000501](https://openairdocs.org/sdr/UIEA2020032000501), Mar 19, 2020: Boeing 76731K. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT EICAS MESSAGE AFTER LANDING, TWO START ATTEMPTS MADE.(

3RD ATTEMPT START SUCCESSFUL. PERFORMED BITE CHECK OF (N1373A) - [SDR UIEA2020031900493](https://openairdocs.org/sdr/UIEA2020031900493), Mar 17, 2020: Boeing 76731K. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT AFTER TAXI TO GATE.(

PERFORMED APU START I/A/W AMM 49-11-00. NO DEFECTS NOTED, OPS CHECK NORMAL.

) (N1487A) - [SDR UIEA2020031100430](https://openairdocs.org/sdr/UIEA2020031100430), Mar 11, 2020: Boeing 76731K. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT, SECOND ATTEMPT SUCCESSFUL.(

PERFORMED APU ECU BITE PROCEDURE IAW AMM 49-61-05, NO FAULTS FOUND. ALL TESTS C (N1373A) - [SDR ASAA2020030932387](https://openairdocs.org/sdr/ASAA2020030932387), Mar 6, 2020: Boeing 737990ER. WARNING SYSTEM. FALSE ACTIVATION. APU "FAULT" LIGHT ILLUMINATED AT APU START PER QRH ATTEMPTED 2ND START AFTER FAULT LIGHT EXTINGUISHED 2ND STARTED SUCCES (N462AS) - [SDR ASAA2020030232300](https://openairdocs.org/sdr/ASAA2020030232300), Feb 26, 2020: Airbus A320214. SENSOR. MALFUNCTIONED. APU AUTO SHUT DOWN, TWO ATTEMPTS. HAS HISTORY GROUNDED - YES. TURN APU MASTER SWITCH ON DO NOT START ACCESS APU SHUTDOWN (N286VA) - [SDR ASAA2020021863200](https://openairdocs.org/sdr/ASAA2020021863200), Feb 16, 2020: Boeing 737990ER. FAULT LIGHT. FALSE ACTIVATION. APU FAULT LT ILLUMINATED ON 1ST ATTEMPT AT 340 APU FAULT LT ILLUMINATED ON 2ND ATTEMPT AT 360 3RD ATTEMP AT 340 - PASSED (N402AS) - [SDR ASAA2020021843201](https://openairdocs.org/sdr/ASAA2020021843201), Feb 14, 2020: Boeing 737990ER. FAULT LIGHT. FALSE ACTIVATION. APU FAULT ILLUMINATED WHEN ATTEMPTING START AFTER LANDING 2ND TRY SUCCESSFUL. GROUNDED - YES. APU STARTS NORMAL NO FAULT (N462AS) - [SDR ASAA2020010931788](https://openairdocs.org/sdr/ASAA2020010931788), Jan 5, 2020: Boeing 737990ER. WARNING SYSTEM. FALSE ACTIVATION. UPON LANDING AND STARTING APU, "FAULT" LIGHT ILLUMINATED. GROUNDED - YES. UPON ARRIVING TO AIRCRAFT, STARTED APU FOUR TI (N462AS) - [SDR UIEA2019112535950](https://openairdocs.org/sdr/UIEA2019112535950), Nov 23, 2019: Boeing 76731K. WARNING MESSAGE. FALSE ACTIVATION. APU FAULT.(

PERFORMED BITE CHECK OF THE APU IAW FIM 49-11 FT 987, MESSAGE CLEARED.

) (N1487A) - [SDR ASAA2019103081176](https://openairdocs.org/sdr/ASAA2019103081176), Oct 28, 2019: Boeing 737990ER. MODULE. FAULTED. APU CSS FAILED FL350, FL350 AND FL310. APU FAULT LIGHT ILLUMINATED. APU OPERATES NORMALLY ON THE GROUND. GROUNDED - YES. (N419AS) - [SDR HALA2019092400384](https://openairdocs.org/sdr/HALA2019092400384), Sep 24, 2019: Airbus A330243. SENSOR. MALFUNCTIONED. ETOPS SIGNIFICANT SYSTEM - APU FAULT AUTO SHUTDOWN ON TAXI IN. REMOVED AND REPLACED APU HIGH OIL TEMP SENSOR PER AMM 49- (N360HA) - [SDR UIEA2019092505573](https://openairdocs.org/sdr/UIEA2019092505573), Sep 24, 2019: Boeing 767306. WARNING SYSTEM. FALSE ACTIVATION. MAINT MSG, APU DOOR. IMPROPER APU SHUTDOWN. CLOSED APU DOOR, APU START NORMAL IAW AMM 49-11-00. (N1321A) - [SDR ASAA2019092130776](https://openairdocs.org/sdr/ASAA2019092130776), Sep 21, 2019: Boeing 737990ER. WARNING SYSTEM. FALSE ACTIVATION. FAULT LIGHT ILLUMINATED DURING APU START ATTEMPT AT FL 340. GROUNDED - YES. ACCOMPLISHED FIM 49-30 TASK 804 INITIAL EVAL (N472AS) - [SDR UIEA2019091605513](https://openairdocs.org/sdr/UIEA2019091605513), Sep 15, 2019: Boeing 76731K. WARNING SYSTEM. FALSE ACTIVATION. EICAS MSG: APU FAULT. PERFORMED BITE OF APU ECU, NO FAULTS FOUND. OPS CHECK GOOD REF AMM 49-61-05. (N1487A) - [SDR HNAA2019091300268](https://openairdocs.org/sdr/HNAA2019091300268), Sep 12, 2019: Emb EMB145LR. WARNING SYSTEM. FALSE ACTIVATION. PDIS 624 49-10 1881591 12SEP19 PHL CLOSE APU FAIL MESSAGE ON EICAS. 28876 00 MDC FACT 12SEP19 19:23 PHL PERFORMED ELECTR (N624AE) - [SDR UIEA2019090905473](https://openairdocs.org/sdr/UIEA2019090905473), Sep 9, 2019: Boeing 7673Y0. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT MESSAGE ON LOWER EICAS. PERFORMED APU CONTROL UNIT BITE TEST IAW AMM 49-61-05 - FAULT NO LONGER PRESENT. PERFO (N1619A) - [SDR UIEA2019090705455](https://openairdocs.org/sdr/UIEA2019090705455), Sep 7, 2019: Boeing 767324. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT, 3RD ATTEMPT AT 17:23Z. CLEARED FAULT. OPS CHECK COMPLIED WITH, APU START IAW 49-60-00. (N645GT) - [SDR UIEA2019083105418](https://openairdocs.org/sdr/UIEA2019083105418), Aug 31, 2019: Boeing 767328. UNKNOWN. MALFUNCTIONED. APU FAULT X3. PERFORMED APU/ECU BITE CHECK PER FIM 49-11-00. NO FAULTS FOUND AT THIS TIME. (N1499A) - [SDR ASAA2019072930233](https://openairdocs.org/sdr/ASAA2019072930233), Jul 29, 2019: Boeing 737890. STATUS MESSAGE. FALSE ACTIVATION. FOUND APU CURRENT STATUS MESSAGE 49-94304. NO APU START FAULTS FOUND. APU STARTED AND RAN NORMALLY. GROUNDED - YES. PER (N566AS) - [SDR ASAA2019072830232](https://openairdocs.org/sdr/ASAA2019072830232), Jul 28, 2019: Boeing 737890. SENSOR. CORRODED. APU TREND DATA SHOWS CT5ATP TEMP IS AT OR ABOVE THE THRESHOLD 605 DEGREES GROUNDED - YES. NO RECENT RELATED MTX MESSAGES (N596AS) - [SDR UIEA2019071904794](https://openairdocs.org/sdr/UIEA2019071904794), Jul 19, 2019: Boeing 76731K. WARNING SYSTEM. FALSE ACTIVATION. APU FAULT EICAS MESSAGE. (

PERFORMED ECU BITE IAW AMM 49-61-05, NO FAULTS NOTED. TEST OK, APU START 2ND ATTEMPT. PILOT (N1487A) All 272: https://openairdocs.org/jasc/4970/reports.md ## Other codes in chapter 49 - [JASC 4900](https://openairdocs.org/jasc/4900): Airborne Auxiliary Power Unit (APU) System (1,839 reports) - [JASC 4910](https://openairdocs.org/jasc/4910): APU Cowling/Containment (953 reports) - [JASC 4920](https://openairdocs.org/jasc/4920): APU Core Engine (2,429 reports) - [JASC 4930](https://openairdocs.org/jasc/4930): APU Engine Fuel and Control (1,087 reports) - [JASC 4940](https://openairdocs.org/jasc/4940): APU Start/Ignition System (1,424 reports) - [JASC 4950](https://openairdocs.org/jasc/4950): APU Bleed Air System (949 reports) - [JASC 4960](https://openairdocs.org/jasc/4960): APU Controls (383 reports) - [JASC 4980](https://openairdocs.org/jasc/4980): APU Exhaust System (164 reports) - [JASC 4990](https://openairdocs.org/jasc/4990): APU Oil System (2,650 reports) - [JASC 4997](https://openairdocs.org/jasc/4997): APU System Wiring (226 reports) --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.