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

NOTE: If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ).

Clear the DTCs with the HDS.
Turn the ignition switch to LOCK (0), and then back to ON (II).
Wait for at least 6 seconds.
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.
Turn the ignition switch to LOCK (0).

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 REFERENCE CHART

Control Unit

Connector

Passenger's MICU

Passenger's under-dash fuse/relay box connector A (38P)

Door multiplex control unit

Power window master switch 37P connector

Gauge control module

32P connector

Immobilizer-keyless control unit

7P connector

Audio unit⁽⁵⁾

Connector B (20P)

Climate control unit

Connector B (12P)

Power seat control unit⁽¹⁾

40P connector

HandsFreeLink control unit

28P connector

AcuraLink control unit⁽²⁾

Connector A (32P)

Audio-navigation unit⁽³⁾

Connector D (20P)

Navigation display unit⁽³⁾

28P connector

Power tailgate control unit⁽⁴⁾

Connector C (14P)

⁽¹⁾

With DPMS

⁽²⁾	With AcuraLink

⁽³⁾	With navigation

⁽⁴⁾	With power tailgate

⁽⁵⁾	Without navigation

Is DTC U1280 indicated with each individual unit disconnected?

YES -Leave the connectors disconnected, and 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 MICU INPUT TEST )
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 )
AcuraLink control unit input test (see MESSAGE DELETE PROCEDURE )
Audio unit input test (see AUDIO UNIT CONNECTOR FOR INPUTS AND OUTPUTS (WITH ELS AUDIO) )
Audio-navigation unit input test (see AUDIO-NAVIGATION SWITCH PANEL FOR INPUTS AND OUTPUTS (WITH ELS AUDIO) )
Navigation display unit input test (see NAVIGATION UNIT CONNECTOR FOR INPUTS AND OUTPUTS )
Power tailgate control unit input test (see CONTROL UNIT INPUT TEST/REPLACEMENT )

Turn the ignition switch to LOCK (0).
Disconnect driver's under-dash fuse/relay box connector P (20P).
Check for continuity between driver's under-dash fuse/relay box connector P (20P) terminals No. 5 and No. 6.
DRIVER'S UNDER-DASH FUSE/RELAY BOX CONNECTOR P (20P)

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 in the B-CAN wires.

NO -Go to step 10.
Check for continuity between body ground and driver's under-dash fuse/relay box connector P (20P) terminals No. 5 and No. 6 individually.
DRIVER'S UNDER-DASH FUSE/RELAY BOX CONNECTOR P (20P)

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(s).

NO -Go to step 11.
Turn the ignition switch to ON (II).
Measure the voltage between body ground and driver's under-dash fuse/relay box connector P (20P) terminals No. 5 and No. 6 individually.
DRIVER'S UNDER-DASH FUSE/RELAY BOX CONNECTOR P (20P)

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(s).

NO -Faulty driver's MICU, replace the driver's under-dash fuse/relay box, USA models (see DRIVER'S UNDER-DASH FUSE/RELAY BOX (MICU)REMOVAL AND INSTALLATION ), Canada models (see SPECIAL TOOLS REQUIRED ).