DTC U1280: Communication bus Line Error (BUS-OFF)

1. Clear the DTCs with the HDS
2. Turn the ignition switch to LOCK (0) and then back to ON (II)
3. Wait for 6 seconds or more
4. Check for DTCs with the HDS

   Is DTC U1280 indicated? 

   YES  -Go to step 5

   NO  -Intermittent failure, the system is OK at this time Check for loose or poor connections, or worn/shorted wires If the connections are good, check the battery condition (see BATTERY TEST ) and the charging system

5. Turn the ignition switch to LOCK (0)
6. Disconnect the appropriate connector at each control unit in the table one at a time Clear the DTC, then recheck for DTCs after each unit is disconnected
   CONTROL UNIT CONNECTOR REFERENCE CHART
   
   

   Control Unit	Connector
   Passenger's MICU	Passenger's under-dash fuse/relay box connector A (38P)
   Door multiplex control unit	37P connector
   Gauge control module	32P connector
   Immobilizer-keyless control unit	7P connector
   Audio unit	Connector B (20P)
   Climate control unit	Connector B(12P)
   Power seat control unit(1)	40P connector
   HandsFreeLink control unit(2)	28P connector
   AcuraLink control unit(3)	Connector A (32P)
   (1) With DPMS (2) With HandsFreeLink (3) With AcuraLink

   Is DTC U1280 indicated with each individual unit disconnected? 

   YES  -Go to step 7

   NO  -Go to the input test (or circuit troubleshooting) for the control unit that was disconnected when DTC U1280 did not reset and perform all power and ground input tests If the tests prove OK, replace that unit

   • Passenger's MICU input test (see COMPONENT LOCATION INDEX )
   • Door multiplex control unit input test (see POWER WINDOW MASTER SWITCH INPUT TEST )
   • Gauge control unit input test (see GAUGE CONTROL MODULE INPUT TEST )
   • Immobilizer-keyless control unit input test (see IMMOBILIZER-KEYLESS CONTROL UNIT INPUT TEST )
   • Climate control unit power and ground circuit troubleshooting (see CLIMATE CONTROL POWER AND GROUND CIRCUIT TROUBLESHOOTING )
   • Power seat control unit input test (see POWER SEAT CONTROL UNIT INPUT TEST/REPLACEMENT )
   • HandsFreeLink control unit input test (see CONTROL UNIT INPUT TEST/REPLACEMENT )
   • AcuraLink control unit input test (see ACURALINK CONTROL UNIT (XM RECEIVER) CONNECTOR FOR INPUTS AND OUTPUTS (WITH ACURALINK) )
   • Audio unit input test (see AUDIO UNIT CONNECTOR FOR INPUTS AND OUTPUTS )
7. Turn the ignition switch to LOCK (0)
8. Disconnect each control unit connector in the table
   CONTROL UNIT CONNECTOR REFERENCE CHART
   
   

   Control Unit	Connector
   Passenger's MICU	Passenger's under-dash fuse/relay box connector A (38P)
   Door multiplex control unit	37P connector
   Gauge control module	32P connector
   Immobilizer-keyless control unit	7P connector
   Audio unit	Connector B (20P)
   Climate control unit	Connector B (12P)
   Power seat control unit(1)	40P connector
   HandsFreeLink control unit(2)	28P connector
   AcuraLink control unit(3)	Connector A (32P)
   (1) With DPMS (2) With HandsFreeLink (3) With AcuraLink

9. Disconnect driver's under-dash fuse/relay box connector P (20P)
10. Check for continuity between driver's under-dash fuse/relay box connector P (20P) terminals No 5 and No 6
    Fig 1: Checking Continuity Between Driver's Under-Dash Fuse/Relay Box Connector P (20P) Terminals No 5 And No 6

    Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Repair a short between the B-CAN wires

    NO  -Go to step 11

11. Check for continuity between body ground and the driver's under-dash fuse/relay box connector P (20P) terminals No 5 and No 6 individually
    Fig 2: Checking Continuity Between Body Ground And Driver's Under-Dash Fuse/Relay Box Connector P (20P) Terminals No 5 And No 6

    Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Repair a short to ground in the wire

    NO  -Go to step 12

12. Turn the ignition switch to ON (II).
13. Measure the voltage between body ground and the driver's under-dash fuse/relay box connector P (20P) terminals No 5 and No 6 individually
Fig 3: Measuring Voltage Between Body Ground And Driver's Under-Dash Fuse/Relay Box Connector P (20P) Terminals No 5 And No 6
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there voltage? 

YES  -Repair a short to power in the wire

NO  -Faulty driver's MICU, replace the driver's under-dash fuse/relay box (see DRIVER'S UNDER-DASH FUSE/RELAY BOX (MICU) REMOVAL/INSTALLATION )