Failure of the GCU 1

TASK 24-20-00-810-868-A
Failure of the GCU 1

1. Possible Causes

GCU-1 [1XU1]
IDG-ENG 1 [4000XU1]
IDG [4000XU]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 24-21-51-000-040	Removal of the Integrated Drive Generator - IDG 1(2)
AMM 24-21-51-000-803	Removal of the Integrated Drive Generator - IDG 1(2)
AMM 24-21-51-400-040	Installation of the Integrated Drive Generator - IDG 1(2)
AMM 24-21-51-400-803	Installation of the Integrated Drive Generator - IDG 1(2)
AMM 24-22-34-000-001	Removal of the GCU-1(2)
AMM 24-22-34-400-001	Installation of the GCU-1(2)
AMM 24-41-00-740-002	Operational Check of the GAPCU via the CFDS

3. Fault Confirmation
Subtask 24-20-00-740-050-A ** ON A/C NOT FOR ALL

A. Test
(1) Do the BITE test of the GAPCU AMM 24-41-00-740-002.
(a) If the BITE test gives the message TEST FAILED:

do the trouble shooting given in Para 4.A.

(b) If the BITE test gives the message TEST PASSED:

stop the trouble shooting.

4. Fault Isolation
Subtask 24-20-00-810-117-D ** ON A/C NOT FOR ALL

A. If the BITE test gives the message TEST FAILED:

Push the line key adjacent to the TEST FAILED message.

(1) If the maintenance message GCU1 (1XU1) comes into view associated with the fault code 121 (SRD FLD (+) FAIL keyword) or 188 (EX FLD (+) SENSE keyword):

Replace GCU-1 [1XU1] AMM 24-22-34-000-001 and AMM 24-22-34-400-001.

(a) If the fault continues:

Replace IDG-ENG 1 [4000XU1] AMM 24-21-51-000-803 and AMM 24-21-51-400-803.

(2) If the maintenance message GCU1 (1XU1) comes into view associated with other fault codes:

Replace GCU-1 [1XU1] AMM 24-22-34-000-001 and AMM 24-22-34-400-001.

Subtask 24-20-00-810-117-G ** ON A/C NOT FOR ALL

A. If the BITE test gives the message TEST FAILED:

push the line key adjacent to the TEST FAILED message.

(1) If the maintenance message GCU1 (1XU1) comes into view associated with the fault code 121 (SRD FLD (+) FAIL keyword) or 188 (EX FLD (+) SENSE keyword):

replace the GCU-1 [1XU1] AMM 24-22-34-000-001 and AMM 24-22-34-400-001.

(a) If the fault continues:

replace the engine 1 IDG [4000XU] AMM 24-21-51-000-040 and AMM 24-21-51-400-040.

(2) If the maintenance message GCU1 (1XU1) comes into view associated with other fault codes:

replace the GCU-1 [1XU1] AMM 24-22-34-000-001 and AMM 24-22-34-400-001.

Subtask 24-20-00-740-051-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:26:16 UTC