04/07/21
Message Overview:
Message Description:
Maintenance Diagnostic Computer (MDC)-1 data bus is not received at Right Input/Output Concentrator (R-IOC).
Possible Causes:
- Maintenance Diagnostic Computer (MDC) (A4-MDC)
- Right Input/Output Concentrator Unit (IOC) 2 (A4-IOC2)
- Integrated Avionics Processing System (IAPS) Card Cage (ICC) (A4)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter: None
NOTE: The IOC has a tri-color LED indicator that is visible when the ICC cover is removed. The three colors are red, green, and amber (both red and green on). The microprocessor sets the following indicated states of the LED:
- Steady red upon power-up reset
- Stead red if the IOC detects an internal failure
- OFF for all internal monitors OK
- OFF if the IOC detects a failure that is not 100% internal to the IOC
- Steady amber while the IOC is being programmed.
Quick Links:
| Operational Test of the Integrated-Avionics Processor System (IAPS) | AMM 31-45-00-710-801 |
| Removal of the Integrated-Avionics Processor System (IAPS) Card Cage (ICC) | AMM 31-45-01-000-801 |
| Installation of the Integrated-Avionics Processor System (IAPS) Card Cage (ICC) | AMM 31-45-01-400-801 |
| 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 |
| Operational Test of the Input/Output Concentrator Unit (IOC) | AMM 31-45-05-710-801 |
| Operational Test of the Maintenance Diagnostic System | AMM 45-45-00-710-801 |
| Removal of the Maintenance Diagnostic Computer (MDC) | AMM 45-45-01-000-801 |
| Installation of the Maintenance Diagnostic Computer (MDC) | AMM 45-45-01-400-801 |
| Wiring - Maintenance Practices - ALL | SPM 20-12-00-02 |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 |
| Electrical Connectors - Maintenance Practice - ALL | SPM 20-20-00-02 |
Troubleshooting Recommendations:
- Reset R IAPS Circuit Breaker CB2-B6. Is the fault message still present?
- If NO, do close out.
- If YES, continue with next step.
- Ring-out MDC1 ARINC Hi-speed bus wiring to left and right IOCs. Ensure there are no shorted lines that may cause damage to the IOCs when swapped. Do wiring check for IAPS Card Cage (A4) L(R) IOC and MDC for the following wires:
From To Expected Result Result MDC A4J17-Pin A47 (L) IOC 1 A4J11-Pin B41 (L) 0 Ω MDC A4J17-PinB47 (H) IOC 1 A4J11-PinA41 (H) 0 Ω MDC A4J17-Pin A47 (L) IOC 2 A4J17-Pin B41 (L) 0 Ω MDC A4J17-PinB47 (H) IOC 2 A4J17-PinA41 (H) 0 Ω MDC A4J17-Pin A47 (L) IOC 1 A4J11-Pin A41 (H) Open MDC A4J17-PinB47 (H) IOC 1 A4J11-PinB41 (L) Open MDC A4J17-Pin A47 (L) IOC 2 A4J17-Pin A41 (H) Open MDC A4J17-PinB47 (H) IOC 2 A4J17-PinB41 (L) Open - If check is satisfactory, continue with next step.
- If check is not satisfactory, repair defective wiring/connectors or replace IAPS Card Cage (A4).
- Swap the Right IOC with the Left IOC. Is the fault message still present?
- If NO, do close out.
- If YES, replace defective IOC.
- Replace MDC. Is the fault message still present?
- If NO, do close out.
- If YES, continue with next step.
- Replace IAPS Card Cage (A4).
- Do close out.
