DC BUS 2 FAIL
(Caution)

Fault is reported by DCPC  when DC BUS 2 is not powered or DC BUS 2 is isolated by Primary Logic cards due to BUS fault detection.

• DC Power Center (DCPC) Contactor (K4)
• DC Power Center (DCPC) Electronic Module (EM2)
• DC Power Center (DCPC) SPDA Feeder Assembly DC BUS 2 Card
• DC Power Center (DCPC) (A63)

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Troubleshoot other related electrical system CAIMS messages before.

NOTE: Verify BUS status on both pilot and copilot EMS CDUs.

1. In CAIMS, SYSTEM DIAG, ATA 24, DC POWER CENTER DCPC_A, LRU TEST, DC POWER DISTRIBUTION page 3. Check the status of TLC 4.

   1. If status is closed, continue with next step.
   2. If status is open continue with step 3.

2. Open DCPC contactor assembly cover and access K4. Check for 28 VDC input on A1 and output on terminal A2.
   
   

   1. If voltage is present on A1 but not on A2, replace contactor K4.
   2. If voltage is present on A1 and A2 continue with step 5.

3. Shut down aircraft power, disconnect P204 from contactor K4 and apply power to the aircraft. Make sure 28 VDC is present on pin 1.
   
   

   1. If 28 VDC is not present, continue with step 4.
   2. If 28 VDC is present, replace contactor.

4. Replace Electronic Module EM2.

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

5. Swap SPDA Feeder Assembly DC BUS 2 (Card 2) Card with DC BUS 1 (card 1).

   1. If fault follows, replace faulty Feeder card.
   2. If fault remains, replace EM2 if not already done.
   3. If fault remains and EM2 has been replaced, continue with next step.

6. Replace DCPC.
7. Do close out.