Loss of the Bus Output from the GPCU to the CFDIU

TASK 31-32-00-810-812-A
Loss of the Bus Output from the GPCU to the CFDIU

1. Possible Causes

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 24-00-00-810-803-A	Circuit Breaker Tripped and/or C/B TRIPPED Warning
ASM 244100
AMM 24-41-34-000-001	Removal of the Ground Power Control Unit (GPCU)
AMM 24-41-34-400-001	Installation of the Ground Power Control Unit (GPCU)
AMM 31-32-00-869-002	Procedure for the Class 3 Fault Reading
ASM 313206
AMM 31-32-34-000-001	Removal of the CFDIU
AMM 31-32-34-400-001	Installation of the CFDIU

3. Fault Confirmation
Subtask 31-32-00-865-059-A ** ON A/C NOT FOR ALL

A. Make sure that this(these) circuit breaker(s) is(are) closed:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
122VU	ELEC/EXT PWR/CTL	11XG	X29
122VU	ELEC/GPCU	7XG	Y24
123VU	GND/PWR/PROT	2XG	AB07

Subtask 31-32-00-740-070-A ** ON A/C NOT FOR ALL

B. On the CFDS MENU page, get access to the class 3 faults reading page AMM 31-32-00-869-002.

4. Fault Isolation
Subtask 31-32-00-810-060-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message:

NO GPCU DATA.

(1) If the circuit breaker (11PB) is tripped:

Do the trouble shooting procedure related to the tripped circuit breaker (Ref. TSM TASK 24-00-00-810-803).

(a) If the fault continues:

1 If the fault continues:

Do a check and repair the wiring from the CFDIU (1TW) pins AA/6F, 6G to the GPCU (1XG) pins AA/7D, 7C ASM 313206.

a If the fault continues:

Subtask 31-32-00-810-196-A ** ON A/C NOT FOR ALL

B. If the fault continues:

(1) If there is 28VDC:

(2) If there is no 28VDC:

Do a check for open or short to ground of the wiring between the circuit breaker C/B-ELEC/GPCU [7XG] and the GPCU [1XG] pin AB/15A.

(a) If there is an open or a short to ground:

(b) If there is no open or short to ground:

Subtask 31-32-00-740-071-A ** ON A/C NOT FOR ALL

C. Do the test given in Para. 3.B.

[Rev.8 from Aug 2018] 2026.04.04 04:29:48 UTC