03/24/21
Message Overview:
Message Description:
DCU Ch. A data bus (A-DCU-2) is reported absent by the left MFD, while it is not reported absent by at least 2 of the following: Left PFD, right MFD and right PFD.
Possible Causes:
- Adaptive Flight-Display Unit 'A429 Input' (L MFD) (A29)
- Junction Box 2 (JB2)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter: None
Quick Links:
| Removal of the Junction Box JB2 | AMM 24-63-05-000-803 |
| Installation of the Junction Box JB2 | AMM 24-63-05-400-803 |
| Removal of the Data Concentrator Unit | AMM 31-41-01-000-802 |
| Installation of the Data Concentrator Unit | AMM 31-41-01-400-802 |
| Removal of the Adaptive Flight-Display Unit | AMM 31-61-01-000-801 |
| Installation of the Adaptive Flight-Display Unit | AMM 31-61-01-400-801 |
| Wiring - Maintenance Practices - ALL | SPM 20-12-00-02 |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 |
| Electrical Connectors - Maintenance Practices - ALL | SPM 20-20-00-02 |
Troubleshooting Recommendations:
- Reset L MFD Circuit Breaker CB1-C5. Is the fault message still present?
- If NO, do close out.
- If YES, continue with next step.
- Swap L MFD (A29) with L PFD (A27). Is the fault message still present?
- If NO, do close out.
- If YES, continue with next step.
- Do wiring check between L MFD (A29), through JB2, and the other AFDs for the following wires:
From: To: Result: Conn. A29P1 - 59 Conn. A26P1 - 59 Conn. A29P1 - 69 Conn. A26P1 - 69 Conn. A29P1 - 59 Conn. A27P1 - 59 Conn. A29P1 - 69 Conn. A27P1 - 69 Conn. A29P1 - 59 Conn. A28P1 - 59 Conn. A29P1 - 69 Conn. A28P1 - 69 - If the check is not satisfactory, repair defective wiring or replace defective JB2.
- If the check is satisfactory, continue with next step.
- Do close out.