Fault Message:

L ITT SIGNAL CH B RNG

Fault Code:

7325726LBR

Associated CAS:

None

There is a failure of the signals from channel B of the Inter-Turbine Temperature (ITT) Thermocouples. The ITT circuits are continuously monitored by the Full-Authority Digital Engine-Controller (FADEC).

• Inter-Turbine Temperature (ITT) Thermocouple
• Left Engine Electronic Controller (EEC)
• 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. 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
   ENGINE	L T/R CTL VALVE	BATT
   ENGINE	L T/R LOWER LOCK	BATT
   ENGINE	L T/R UPPER LOCK	BATT

2. Perform a deactivation of the thrust reverser and open the cowls.
3. Remove the applicable bypass-duct access panel and the applicable combustion section fairing.

   1. If the fault message is stored, fault could be intermittent.
   2. If the fault message is not stored, continue with next step.

4. Examine the interface wiring for damage between the connectors and the terminal blocks that follow:

   • The EEC connector P1047
   • The bypass duct connectors J1032 and P1032
   • The terminal blocks TB2215, TB2216 and the ground connector GC2203
   • The Alumel and Chromel connector posts on the ITT thermocouples
     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.
     NOTE: Look specially for signs of damage adjacent to clip locations.

   1. If there is damage, repair defective wiring as required and go to step 14.
   2. If there is no damage, 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 14.
   2. If the fault message is active, continue with next step.

6. Perform the fault isolation for the ITT signal.
7. Disconnect the EEC connector P1044 and the bypass duct connector P1030. Disconnect the interface wiring at the terminal blocks TB2112, TB2113 and at the ground connector GC2103.
8. Examine the interface wiring and connectors for damage between the connectors and the terminal blocks that follow:

   • The EEC connector P1047
   • The bypass duct connectors J1032 and P1032
   • The terminal blocks TB2215, TB2216 and the ground connector GC2203
   • The Alumel and Chromel connector posts on the ITT thermocouples
     NOTE: Look specially for signs of chafing adjacent to clip locations, condition of connector pins and wiring kink or strain.

   1. If there is no damage, repair defective wiring as required and go to step 14.
   2. If there is damage, continue with next step.

9. Clean the terminal blocks TB2215, TB2216 and the ground connector GC2203.
10. Perform wiring checks between TB2215 and Bypass Duct (P1032).

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

11. Perform wiring checks between TB2216 and Bypass Duct (P1032).

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

12. Perform wiring checks between Bypass Duct (J1032) and EEC (P1047).

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

13. Install the applicable combustion section fairing and the applicable bypass-duct access panel.
14. Close the cowls and perform the activation of the thrust reverser.
15. Close 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
    ENGINE	L T/R CTL VALVE	BATT
    ENGINE	L T/R LOWER LOCK	BATT
    ENGINE	L T/R UPPER LOCK	BATT

    1. If the fault message stays active, replace the ITT harness and do close out.
    2. If the fault message stays inactive, continue with next step.

16. Replace the Left EEC.
17. Make sure that the primary indication of ITT shows on the EICAS display.
18. Do close out.