Message Name:

T2 HEAT CURRENT SENSE 1A

Message Code:

B3-303022

Associated CAS:

None

• TT2 Heat Current Sense 1A
• Wiring Harness (W1)
• TT2 Current Sense Relay in the Aircraft DC Power Center (DCPC)
• Full Authority Digital Engine Control Unit (FADEC) Electronic Control Unit A (ECU) (A41)

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. If the L or R ENGINE FAULT CAS message is shown with this fault, this is a No Dispatch condition.
2. If there is not a L or R ENGINE FAULT CAS message, only a MCID or fault equation, then this is a Long Term Dispatch (LT) fault and is subject to correction outlined in the Honeywell LEMM SUB TASK 5-10-00-200-003.
3. 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.

Check MCID for faults, if 805 is listed, work that first. If MCID post a 803, or 804 fault only, troubleshoot using the following steps for aircraft and engine fault isolation with reference to the Light Engine Maintenance Manual TASK 72-00-00-810-111.

1. Check and reset Circuit Breaker CB1-E11.
2. Check & verify the system operation IAW AMM TASK 30-21-00-710-801, look for the system fault by viewing the ANTI-ICE synoptic page looking for the amber T2 fault. If the fault still exists, continue, otherwise closeout.
3. With a meter, verify and ring the TT2 sense output from the Left DC Power Center A35P3 pin 33 to W6P3/A43J2 pin 63, repair wiring if required per the wiring manual standard practices. If the wiring checks good, remove and replace the right DC power center PCB1 protection card IAW AMM TASK 24-61-77-000-801, TASK 24-61-77-400-801. Recheck the system IAW AMM TASK 30-21-00-710-801.
4. If the fault still exists, suspect the Electronic Control Unit, remove and replace IAW AMM TASK 76-10-05-000-801, TASK 76-10-05-400-801.

If MCID is listing both 803 ECU A fault, and 804 ECU B faults:

1. Check & verify the system operation IAW AMM TASK 30-21-00-710-801, look for the system fault by viewing the ANTI-ICE synoptic page looking for the amber T2 fault. If the fault still exists, continue, otherwise closeout.
2. Check the TT2 probe heater for continuity, check resistance from the Left DC Power Center A35P3 pin 33 to W6P2/A41J2 pin 63, and Right DC Power Center A35P3 pin 8 to W6P2/A43J2 pin 63, there should be continuity < 0.1Ω, repair wiring if required per the wiring manual standard practices.
3. If there is not continuity, gain access to the following connectors, inspect for damage, then check the following segments per the table, repair wiring if required per the wiring manual standard practices:

   From	To	Value
   TT2 Sensor Pin 5	TT2 Sensor Pin 6	≈ 5 to 30Ω
   W6P7 Pin 6	Ground	<.01Ω
   W6P7 Pin 5	A35P3 Pin 52	<.01Ω

4. With a meter, verify and ring-out the TT2 sense output from the Left DC Power Center A35P3 to the ECU Channel A & B.
   

   From	To	Value
   A35P3 Pin 8	W6P3/A41J1 Pin 63	<.01Ω
   A35P3 Pin 33	W6P2/A43J2 Pin 63	<.01Ω

5. If the wiring checks good, remove and replace the DC power center PCB1 protection card IAW AMM TASK 24-61-77-000-801, TASK 24-61-77-400-801. Recheck the system IAW AMM TASK 30-21-00-710-801.