03/15/21
Message Overview:
Message Description:
No PSEU-B transmission or corrupted PSEU-B transmission to Data Concentrator Unit (DCU) and IOC 2. Aircraft wiring or PSEU requires troubleshooting.
Possible Causes:
- Proximity-Sensor Electronic Unit (PSEU) (A9)
- Input/Output Concentrator 2 (IOC 2) (A4-IOC2)
- 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 Input/Output Concentrator Unit (IOC) | AMM 31-45-05-000-801 |
| Installation of the Input/Output Concentrator Unit (IOC) | AMM 31-45-05-400-801 |
| Removal of the Proximity-Sensor Electronic Unit (PSEU) | AMM 32-61-09-000-801 |
| Installation of the Proximity-Sensor Electronic Unit (PSEU) | AMM 32-61-09-400-801 |
| Functional Test of the Proximity-Sensor Electronic Unit (PSEU) | AMM 32-61-09-720-801 |
| Standard Practices - Replace Wiring | SPM 20-12-00-02 |
| Standard Practices - Wire Repair | SPM 20-12-10-02 |
Troubleshooting Recommendations:
- Pull and reset the PSEU gear system breakers (CB1-C13, CB1-C14, CB2-C13, CB2-C14), recheck the system for the fault.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Check the ARINC 429 data bus from the PSEU A9AP1 pins 10J, 9J to IAPS A4P101 PINS 61, 62, and PSEU A9AP1 PINS 10J, 9J to DCU PINS A14EP1 3A, 3B. Repair as required.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Reset the circuit breakers R IAPS CB CB2-B6 then look for other failures related to the Input Output Concentrators, swap or replace the IOCs if this is suspected.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- With JB2 connector JB2DP1 check continuity between PIN 12H and 12K and between 12H and 12F. Check continuity between PIN 12J and 13A and between 12J and 12G.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace JB2.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- Replace the PSEU.
- Functional test of the PSEU.


