Loss of GPS Data Detected by the ATSU

TASK 46-21-00-810-848-A
Loss of GPS Data Detected by the ATSU

1. Possible Causes

[1SN2]
ATSU [1TX1]
wiring of the GPSSU2 DATA BUS
MMR-2 [40RT2]
wiring of the MMR2 DATA BUS

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 34-36-31-000-001	Removal of the ILS Receiver
AMM 34-36-31-400-001	Installation of the ILS Receiver
AMM 34-58-31-000-001	Removal of the GPSSU
AMM 34-58-31-400-001	Installation of the GPSSU
AMM 46-21-00-740-001	BITE Test of the ATIMS
AMM 46-21-34-000-001	Removal of the Air Traffic Service Unit (ATSU)
AMM 46-21-34-400-001	Installation of the Air Traffic Service Unit (ATSU)

3. Fault Confirmation
Subtask 46-21-00-740-142-A

A. Test
(1) Do the BITE test of the ATIMS AMM 46-21-00-740-001.

4. Fault Isolation
Subtask 46-21-00-810-098-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message GPSSU2(1SN2)/ATSU1(1TX1):

replace the [1SN2] AMM 34-58-31-000-001 and AMM 34-58-31-400-001.

(1) If the fault continues:

replace the ATSU [1TX1] AMM 46-21-34-000-001 and AMM 46-21-34-400-001.

(a) If the fault continues:

remove the GPSSU2 and the ATSU
do a check and repair the wiring of the GPSSU2 DATA BUS
install the GPSSU2 and the ATSU.

Subtask 46-21-00-810-098-B ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message GPSSU2(1SN2)/ATSU1(1TX1):

replace the MMR-2 [40RT2] AMM 34-36-31-000-001 and AMM 34-36-31-400-001.

(1) If the fault continues:

replace the ATSU [1TX1] AMM 46-21-34-000-001 and AMM 46-21-34-400-001.

(a) If the fault continues:

remove the MMR2 and the ATSU
do a check and repair the wiring of the MMR2 DATA BUS
install the MMR2 and the ATSU.

Subtask 46-21-00-740-143-A

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:34:21 UTC