Fault Message:

L ENG [N1 SPEED PROBE]/WIRING

Fault Code:

7735316BRV

Associated CAS:

None

The fault message is set when there is a problem with the N1 speed input to the Engine Vibration-Monitoring Unit (EVMU).

• N1 Speed Probe
• Engine Vibration-Monitoring Unit (EVMU) (A42)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

CAUTION: DO NOT DO ELECTRICAL CHECKS INTO THE ENGINE ELECTRONIC CONTROLLER (EEC). IF YOU DO NOT OBEY THIS INSTRUCTION, DAMAGE TO THE EEC CAN OCCUR.

1. Remove the electrical power from the aircraft.
2. In the flight compartment, on the EMS CDU, open the circuit breakers that follow:

   System Name	Circuit Breaker Name	Bus Name
   ENGINE	L FADEC CH A	BATT
   ENGINE	L FADEC CH B	BATT
   ENGINE	L ENG IGN 1	BATT
   ENGINE	L ENG IGN 2	BATT
   ENGINE	L ENG FUEL HPSOV	BATT
   ENGINE	L ENG START A	BATT
   ENGINE	L ENG START B	BATT
   THRUST REV	L T/R CTL VALVE	BATT
   THRUST REV	L T/R LOWER LOCK	BATT
   THRUST REV	L T/R UPPER LOCK	BATT

3. Perform a deactivation of the thrust reverser and open the cowls.
4. Perform a visual inspection of the interface wiring, terminals and connectors for damage between EVMU (A42BP1) and N1 speed probes (P711).
   NOTE: Look specially for signs of damage adjacent to clip locations, condition of connector pins and wiring that is kinked or strained.

   1. If any damage found, repair or replace as required and go to step 16.
   2. If no damage and the fault message was stored in the Fault Confirmation above, then the fault could be intermittent and continue with next step.

5. Monitor the system to see if the fault message occurs again.

   1. If the fault message is not active, go to step 16.
   2. If the fault message is active, continue with next step.

6. Perform wiring checks between N1 Speed Probe (P711) and Fixed Cowl Interface (1PB2).

   1. If wiring checks are not good, repair defective wiring as required and go to step 16.
   2. If wiring checks are good, continue with next step.

7. Perform wiring checks between F ixed Cowl Interface (1JB2) and A ft Pressure Bulkhead STN 861 LHS (P607).

   1. If wiring checks are not good, repair defective wiring as required and go to step 16.
   2. If wiring checks are good, continue with next step.

8. Perform wiring checks between Fixed Cowl Interface (2JB2) and A ft Pressure Bulkhead STN 861 RHS (P608).

   1. If wiring checks are not good, repair defective wiring as required and go to step 16.
   2. If wiring checks are good, continue with next step.

9. Perform wiring checks between Aft Pressure Bulkhead STN 861 LHS (J607) and EVMU (A42BP1).

   1. If wiring checks are not good, repair defective wiring as required and go to step 16.
   2. If wiring checks are good, continue with next step.

10. Check for fault message L ENG [N1 SPEED PROBE]/WIRING.

    1. If the fault is not active, go to step 16.
    2. If the fault stays active, continue with next step.

11. Perform a check for the insulation resistance of the interface between the connectors N1 Speed Probe to Fixed Cowl Interface.

    From	To	Expected Result	Result
    P711-1	Ground	>20 megaohms
    P711-2	Ground	>20 megaohms

    1. If the resistance value is out of limit, repair defective wiring as required and go to step 16.
    2. If the resistance value is within limit, continue with next step.

12. Perform a check for the insulation resistance of the interface between the connectors Fixed Cowl Interface to Aft Pressure Bulkhead.

    From	To	Expected Result	Result
    P607-r	Ground	>20 megaohms
    P607-s	Ground	>20 megaohms

    1. If the resistance value is out of limit, repair defective wiring as required and go to step 16.
    2. If the resistance value is within limit, continue with next step.

13. Perform a check for the insulation resistance of the interface between the connectors Aft Pressure Bulkhead to EVMU.

    From	To	Expected Result	Result
    A42BP1-A1	Ground	>20 megaohms
    A42BP1-B1	Ground	>20 megaohms

    1. If the resistance value is out of limit, repair defective wiring as required and go to step 16.
    2. If the resistance value is within limit, continue with next step.

14. Replace EVMU.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

15. Replace the power plant.
16. Close the cowls and activate the Thrust Reverser.
17. Do close out.