03/08/21
Message Overview:
Message Description:
No RB-FADEC bus input to A-DCU and not absent at L-PFD and L-MFD.
Possible Causes:
- Data Concentrator Unit (DCU) (A14)
- Junction Box 4 (JB4)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter: None
Quick Links:
| Removal of the Junction Box JB4 | AMM 24-63-13-000-802 |
| Installation of the Junction Box JB4 | AMM 24-63-13-400-802 |
| Removal of the Data Concentrator Unit (DCU) | AMM 31-41-01-000-802 |
| Installation of the Data Concentrator Unit (DCU) | AMM 31-41-01-400-802 |
| Removal of the Engine Electronic Control Unit (ECU) | AMM 76-10-05-000-801 |
| Installation of the Engine Electronic Control Unit (ECU) | AMM 76-10-05-400-801 |
| Wiring - Maintenance Practices - ALL | SPM 20-12-00-02 |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 |
07/12/19
Troubleshooting Recommendations:
- Reset EICAS DCU A Circuit Breaker CB1-D1 and EICAS DCU B Circuit Breaker CB2-D1. Is the fault message still present?
- If NO, do close out.
- If YES, continue with next step.
- Do wiring check between DCU (A14) and right Engine FADEC channel B (A42), through Junction Box 4 for the following wires:
From To Result Conn. A14EP1 - 4A Conn. W1P2 (at A42) - 45 Conn. A14EP1 - 4B Conn. W1P2 (at A42) - 55 - If the check is satisfactory, continue with next step.
- If the check is not satisfactory, repair defective wire or Junction Box 4.
- Replace DCU (A14).
- Do close out.