APU AUTO SHUTDOWN - SENSOR FAILURE, Both EGT Sensors failed (131-9(A))

TASK 49-00-81-810-816-A
APU AUTO SHUTDOWN - SENSOR FAILURE, Both EGT Sensors failed (131-9(A))

1. Possible Causes

BOTH EGT SENSORS FAILED
EGT 1 and 2 THERMOCOUPLE
aircraft wiring
ELECTRONIC CONTROL BOX [59KD]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 49-00-00-860-008	APU Start by External Power
ASM 496104
AMM 49-61-34-000-003	Removal of the Electronic Control Box (ECB) (131-9(A))
AMM 49-61-34-400-003	Installation of the Electronic Control Box (ECB) (131-9(A))
AMM 49-72-15-000-002	Removal of the Thermocouples (131-9(A))
AMM 49-72-15-400-003	Installation of the Thermocouples (131-9(A))

3. Fault Confirmation
Subtask 49-00-81-710-118-A ** ON A/C NOT FOR ALL

A. Read-out of ECB Trouble-Shooting Data
(1) Put the APU MASTER SW to the ON position.
(2) Get access to the APU SHUTDOWN report.
(3) Push the '>' adjacent to LRU DATA:

the MCDU menu shows
BOTH EGT SENSORS FAILED

(4) Start the APU and apply Bleed Air for 20 seconds, minimum AMM 49-00-00-860-008.

4. Fault Isolation
Subtask 49-00-81-810-090-A ** ON A/C NOT FOR ALL

A. If an APU auto shutdown occurs during the APU operation and the APU SHUTDOWN report gives the maintenance message:

SENSOR FAIL
EGT TCPLE RAKE 1 + 2

associated with Fault Code Number (FCN) 35

replace the EGT 1 and 2 THERMOCOUPLE AMM 49-72-15-000-002 and AMM 49-72-15-400-003.

(1) If the fault continues:

do a check and repair of the aircraft wiring from
the ECB (59KD) AB/A6,A7 to the EGT1 THERMOCOUPLE terminals alumel/chromel
and
the ECB (59KD) AB/A8,A9 to the EGT2 THERMOCOUPLE terminals alumel/chromel ASM 496104.

(2) If the fault continues:

replace the ELECTRONIC CONTROL BOX [59KD] AMM 49-61-34-000-003 and AMM 49-61-34-400-003.

Subtask 49-00-81-810-090-B ** ON A/C NOT FOR ALL

A. If an APU auto shutdown occurs during the APU operation and the APU SHUTDOWN report gives the maintenance message:

SENSOR FAIL
EGT TCPLE RAKES(8057KM1) AND (8057KM2)

associated with Fault Code Number (FCN) 35

replace the EGT 1 and 2 THERMOCOUPLE AMM 49-72-15-000-002 and AMM 49-72-15-400-003.

(1) If the fault continues:

do a check and repair of the aircraft wiring from
the ECB (59KD) AB/A6,A7 to the EGT1 THERMOCOUPLE terminals alumel/chromel
and
the ECB (59KD) AB/A8,A9 to the EGT2 THERMOCOUPLE terminals alumel/chromel ASM 496104.

(2) If the fault continues:

replace the ELECTRONIC CONTROL BOX [59KD] AMM 49-61-34-000-003 and AMM 49-61-34-400-003.

Subtask 49-00-81-710-119-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:34:33 UTC