Fault Message:

GCU2 SENSE/GEN2 CONT SW FAULT

Fault Code:

2422254LPS

Associated CAS:

GEN 2 FAIL
(Advisory)

Generator Control Unit (GCU) 2 has detected a fault in the Generator Control Switch (GCS)/wiring or in its internal GCS sensing circuit.

GCU GCS sensing circuit has detected the OFF signal as being the same as the ON signal.

• Generator Control Unit (GCU) 2 (A57)
• Generator Control Switch (GCS)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

A GCU patch cable (GSE REF # 24X-24-02) can be used to swap GCUs 1, 4 and 5 into position 2 or 3 (for troubleshooting only).

The GCU NVMs can only be downloaded at position #2 or #3.

1. Swap GCU 2 with GCU 3.

   1. If system checks are good, replace the GCU 2 and do close out.
   2. If fault remains, continue with next step.

2. Disconnect both GCU 2 connector A57P2 and overhead control panel connector AP3P1. Perform a wiring check (open circuits check) between interface wiring GCU/Electrical Control Panel as follows:

   From	To	Result
   A57P2-21	AP3P1-K
   A57P2-28	AP3P1-L

   1. If wiring checks are not good, repair wiring as required and do close out.
   2. If wiring checks are good, continue with next step.

3. Perform a wiring check (short circuits check) between interface wiring GCU/Electrical Control Panel as follow:

   From	To	Result
   A57P2-21	Ground
   A57P2-28	Ground

   1. If wiring checks are not good, repair wiring as required and do close out.
   2. If wiring checks are good, continue with next step.

4. Perform a continuity check between the Electrical Control Panel and ground as follows:

   From	To	Result
   AP3P1-J	Ground

   1. If there is continuity, repair wiring as required and do close out.
   2. If there is no continuity, continue with next step.

5. Perform a continuity check between the Electrical Control Panel and ground stud as follows:

   From	To	Result
   AP3P1-J	GS729

   1. If there is continuity, check the integrity of ground stud GS729 and repair wiring as required and do close out.
   2. If there is no continuity, continue with next step.

6. Inspect the electrical control panel internal wiring and the generator control switch (GCS-SDS4).

   1. If wiring checks are not good, repair wiring as required and do close out.
   2. If wiring checks are good, continue with next step.

7. Replace GCS.
8. Do close out.