04/19/21
Message Overview:
Message Description:
Right engine N1 monopole fault 1A.
[MCID 0502]
N1 Monopole 1A.
Detection of a fault in the N1 monopole harness between the N1 monopole and ECU A. ECU A cannot support full system operation.
Possible Causes:
- N1 Monopole
- Wiring Harness (W4)
- Full Authority Digital Engine Control (FADEC) Electronic Control Unit A (ECU) (A40)
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter: None
- If the L or R ENGINE MINOR FAULT CAS message is shown with this fault, this is a Short Term dispatch (STD) fault and is subject to correction outlined in the Honeywell LEMM SUBTASK 5-10-00-200-003.
- If a L or R FADEC FAIL CAS message is shown, this is a No Dispatch (ND) fault and is subject to correction outlined in the Honeywell LEMM SUBTASK 5-10-00-200-003.
- Check for the following MDC messages displayed with the fault: X-channel bus 1A (MCID 0905), X-channel bus 1B (MCID 0906), X-channel discrete 1A (MCID 0933), X-channel discrete 1B (MCID 0934). If any of the above MCID codes are posted, correct the cross channel faults first.
Quick Links:
| 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 |
| Electrical Connectors - Maintenance Practice - ALL | SPM 20-20-00-02 |
Troubleshooting Recommendations:
- MCID 0502 fault only is present, troubleshoot using the following steps for aircraft and engine fault isolation with reference to the Light Engine Maintenance Manual Subtask 72-00-00-810-071-A01.
- Reset and reboot the ECU to recheck the MDC MCID for the posted fault.
- Remove the connector on the ECU 1B W4P13, inspect for burned or pushed back pins/sockets, then check the following segments per the table, repair wiring if required per the wiring manual standard practices.
From To Value W4P13 Pin 43 W4P13 Pin 44 200 to 1,000 Ω W4P13 Pin 51 W4P13 Pin 52 200 to 1,000 Ω - If the resistance values check well, proceed to step 7, if the resistance values were bad at the ECU, perform a resistance check on the N1 monopole as shown in the table below:
From To Value W4P15 Pin 1 W4P15 Pin 2 200 to 1,000 Ω W4P15 Pin 3 W4P15 Pin 4 200 to 1,000 Ω - If the resistance values fail at the N1 sensor, replace the sensor IAW Honeywell LEMM TASK 77-10-01-050-801. If the resistance values check good, suspect the W4 wiring harness and replace per the Honeywell LEMM TASK 76-10-01-050-801.
- If the wiring and monopole check good, consider swapping or replacing the A channel ECUs for the left engine, remove and replace IAW AMM TASK 76-10-05-000-801, TASK 76-10-05-400-801 then recheck the system for the fault.
