Message Name:

AIR TRAFFIC CONTROL (ATC) TRANSPONDER SYSTEM NO DATA

The Air Traffic Control (ATC) Transponder System cannot transmit or receive data.

• Air Traffic Control (ATC) Transponder Module
• Air Traffic Control (ATC) Antenna (Bottom) (E8)
• Air Traffic Control (ATC) Antenna (Bottom) (E9)
• Air Traffic Control (ATC) Antenna (Top) (E10)
• Air Traffic Control (ATC) Antenna (Top) (E11)
• Very High Frequency (VHF) Communication Unit 1 (A1)
• Very High Frequency (VHF) Communication Unit 2 (A2)

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: The optional VHF COM unit 3 does not contain an ATC transponder module.

NOTE: When the radio system is initially energized (after a cold-start and during a WOW condition), it automatically starts the POST. The POST does an RMU test, RSB continuity test, and radio module test. The POST does not do a test of the antennas or coaxial cables.

1. If the RMU display shows CHK NAV 1-2 UNIT on the SYSTEM TEST RESULTS page. Push the TST (test) pushbutton on the RMU to get the RADIO TEST RESULTS page from the SYSTEM TEST RESULTS page. Check if the RMU display shows ATC 1-2 ERR.
   NOTE: If the RMU display shows CHK RMU 1-2, or, if the RMU displays are magenta, perform the troubleshooting for the observed fault Radio Management Units and continue with next step.

   1. If the RMU display does not show DME 1-2 ERR, go to step 3.
   2. If the RMU display shows DME 1-2 ERR, continue with next step.

2. Perform the operational test of the RSB part of the digital bus system. On the CAIMS PMAT, perform the IBIT of the RSB part of the digital bus system.

   1. If the results of the RSB test are not satisfactory, repair or replace the defective RSB wiring as required and do close out.
   2. If the results of the RSB test are satisfactory, continue with next step.

3. On the RMU display, look on the applicable maintenance log page(s) for the messages as follows:

   Event Description	Maintenance Page (Radio or cluster module)	Event Code
   CHK OUTP	Radio	49, 4A, 4B, 4C, 4D
   CODE ERR	Cluster	A5
   COMPUTER	Cluster	06, 07, 08, 09, 86, 87, 88, 89, A4
   COMPUTER	Radio	08, 09, 21, 22, 35, 89, A1, A2, B1, B5, BE
   DATA BUS	Cluster	03, 04, 05, 83, 84, 85
   DATA BUS	Radio	03, 04
   FPGA ERR	Cluster	B0, B6
   INTERFAC	Radio	3D, BD, 3F,BF, C9, CA, CB, CC, CD, E0, E1, E2, E3, E4, E5, E6, E7, E8, E9
   INT TEMP	Radio	26, A6
   PWR SPLY	Radio	25, 27, 28, 29, 37, 38, 39, 58, 2A, 2B, 2C, 2D, 3A, 3B, 3C, A5, A7, A8, A9, B7, B8, B9, D2, D3, D4, D6, D7, D8, D9, AA, AB, AC, AD, BA, BB, BC
   RAM ERR	Cluster	A1, A2, A3, 2A
   RECEIVER	Radio	B0, B6
   RSB PRI	Cluster	AB
   RSB SEC	Cluster	AC
   RSB TX	Cluster	AD, AE
   STRAPS	Cluster	A6
   XMITTER	Radio	2E, 2F, AD, AE, AF, D5

   1. If the messages are not found, do close out.
   2. If one or more of the given messages are found, replace the VHF COM unit 1-2 and continue with next step.

4. On the RMU display, look on the applicable maintenance log page(s) for the message as follows:

   Event Description	Maintenance Page (Radio or cluster module)	Event Code
   STRAPS	Radio	32, 33, 34, 51, B2, B3

   1. If the given message is not found, do close out.
   2. If the given message is found, go to the ATC STRAPS page on the RMU that shows a list of straps that are cut (open) and check that the list of straps is correct for the aircraft configuration and continue with next step.

5. On the RMU display, look on the applicable maintenance log page for the messages as follows:

   Event Description	Maintenance Page (Radio or cluster module)	Event Code
   XMITTER	Radio	23, 24, A3, A4

   1. If the given messages are found, continue with next step.
   2. If the given messages are not found, do close out.

6. Perform a visual inspection of the ATC antennas and related coaxial cables.

   1. If the defective components are not found after the visual inspection, do close out.
   2. If the defective components are found after the visual inspection, replace the DME antenna 1-2-3-4 and Coaxial Cable. Continue with next step.

7. On the RMU display, look on the applicable maintenance log page for the messages as follows:

   Event Description	Maintenance Page (Radio or cluster module)	Event Code
   CHK TCAS	Radio	42
   CHK DLPA	Radio	43
   CHK DLPC	Radio	44
   CHK ADC1	Radio	45
   CHK ADC2	Radio	46
   CHK CTL1	Radio	47
   CHK CTL2	Radio	48

8. Do close out.