Message Name:

TT2 SENSOR/HEATER 4

Message Code:

B3-304646

Associated CAS Messages:

L FADEC FAIL
(Caution)

L ENG A/ICE FAIL ON
(Advisory)

Left engine TT2 sensor/heater fault 4.

[MCID 0805]
TT2 Sensor/Heater 4.
Detection of a fault primarily in the TT2 sensor/heater.

• Wiring Harness (W1)
• Wiring Harness (W6)
• TT2 Current Sense Relay in the DC Power Center (DCPC)
• TT2 Sensor

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 SUBTASK 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.

1. Check MDC for faults, if a MCID 805 is listed, troubleshoot using the following steps for aircraft and engine fault isolation with reference to the Light Engine Maintenance Manual Subtask 72-00-00-810-117-A01.
2. Make sure Circuit Breaker (CB)  CB1-E11 is set to IN.
3. Perform the Operational Test of the Nacelle Anti-Ice System (AMM TASK 30-21-00-710-801). View the ANTI-ICE synoptic page, paying attention for the amber T2 fault. Is the fault still present?
   

   1. If YES, continue with next step.
   2. If NO, do close out.

4. Perform a continuity/resistance check of the TT2 probe heater. Measure the resistance from the Left DC Power Center A35P3 pin 52 to ground, there should be continuity ≈ 5 to 30 Ω.
   

   1. If resistance value is out of tolerance, replace the TT2 sensor.
   2. If there is no continuity, continue with next step.

5. Gain access to the engine connectors listed in the table below. Inspect for proper installation or damage and rectify if required. Perform a wiring check as follows:
   

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

   1. If wiring defects are found, repair defective wiring as required and do close out.
   2. If no defects are found, continue with next step.

6. Perform a continuity check of the TT2 sense output from the Left DC Power Center to the ECU Channel A & B.
   

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

   1. If wiring defects are found, repair defective wiring as required and do close out.
   2. If no defects are found, continue with next step.

7. Replace the DC power center PCB1 protection card.
8. Do close out.