Message Name:

NO R-GP-4 IOC BUS INPUT

Message Code:

B3-006325

Associated CAS:

None

R-GP-4 data bus is reported absent by the Electronic Control Unit (ECU) Auxiliary Power Unit (APU), while R-GP-4 data bus is not reported failed or absent by 2 of the following LRU: Input / Output Concentrator (IOC) 1, Left Engine ECU channel A and Weather Radar.

NOTE: The Weather Radar is a user of the R-GP-4 data bus only for the following Aircraft:

• A/C 20001 and 20002
• A/C 20003 to 20407 pre SB100-34-33
• A/C 20001 to 20407 pre SB100-34-32

• Auxiliary Power Unit (APU) Electronic Control Unit (ECU) (A39)
• Junction Box (JB2)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: The APU Master Switch must be selected at RUN (or START) to provide the primary power and the "Essential Operation" command discrete to the APU ECU.

1. Dowiring check from APU ECU (A39), through Junction Box 2 (JB2), to IAPS Card Cage (A4) for the following wires:

   From	To	Result
   Conn. A39BP1-A9	Conn. A4P101-73
   Conn. A39BP1-A10	Conn. A4P101-74

   1. If the check is satisfactory, continue with next step.
   2. If the check is not satisfactory, repair wiring or defective JB2.
      NOTE: Another LRU receiving the R-GP-4 data bus, instead of the IAPS Card Cage (A4), can also be used to confirm wiring integrity. Refer to wiring diagrams listed above.

2. Replace APU ECU (A39).
3. Do close out.