DTC U1280: Communication Circuit Error (BUS-OFF)

NOTE: If you are troubleshooting multiple DTCs, be sure to follow 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

Connector

Door multiplex control unit

37P connector

Gauge control module

32P connector

Immobilizer-keyless control unit

7P connector

Audio unit⁽¹⁾

Connector D (20P)

Audio-navigation unit⁽²⁾

Connector E (20P)

Navigation display unit⁽²⁾

32P connector

Audio display-USB adapter control unit⁽³⁾

32P connector

Climate control unit⁽⁴⁾

Connector A (36P)

HVAC control unit⁽⁵⁾

Connector A (24P)

Power tailgate control unit⁽⁶⁾

Connector C(14P)

Automatic lighting control unit⁽⁷⁾

14P connector

Power seat control unit⁽⁸⁾

Connector B (40P)

Parking and back-up sensor control unit⁽⁹⁾

24P connector

Seat heater control unit⁽¹⁰⁾

14P connector

⁽¹⁾	Without navigation, with climate control

⁽²⁾	With navigation

⁽³⁾	Without navigation, with USB adapter

⁽⁴⁾	With climate control

⁽⁵⁾	Without climate control

⁽⁶⁾	With power tailgate

⁽⁷⁾	With automatic lighting system

⁽⁸⁾

With DPMS

⁽⁹⁾	With parking and back-up sensor system

⁽¹⁰⁾	With seat heater

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.

Power window master switch input test (see POWER WINDOW MASTER SWITCH INPUT TEST )
Gauge control module input test (see GAUGE CONTROL MODULE INPUT TEST )
Immobilizer-keyless control unit input test (see IMMOBILIZER-KEYLESS CONTROL UNIT INPUT TEST )
Audio unit connector for inputs and outputs (see AUDIO UNIT CONNECTOR FOR INPUTS AND OUTPUTS (WITH CLIMATE CONTROL) )
Audio-navigation unit connector for inputs and outputs (see NAVIGATION UNIT CONNECTOR FOR INPUTS AND OUTPUTS )
Navigation display unit connector for inputs and outputs (see NAVIGATION DISPLAY UNIT CONNECTOR FOR INPUTS AND OUTPUTS )
Audio display-USB adapter control unit connector for inputs and outputs (see AUDIO DISPLAY-USB ADAPTER CONTROL UNIT CONNECTOR FOR INPUTS AND OUTPUTS (WITH USB ADAPTER) )
Climate control unit power and ground circuit troubleshooting (see CLIMATE CONTROL UNIT POWER, GROUND, AND COMMUNICATION CIRCUIT TROUBLESHOOTING )
HVAC control unit power and ground circuit troubleshooting (see HVAC CONTROL POWER, GROUND, AND COMMUNICATION CIRCUIT TROUBLESHOOTING )
Power tailgate control unit input test (see CONTROL UNIT INPUT TEST/REPLACEMENT )
Automatic lighting control unit input test (see AUTOMATIC LIGHTING CONTROL UNIT INPUT TEST/REPLACEMENT )
Power seat control unit input test (see POWER SEAT CONTROL UNIT INPUT TEST/REPLACEMENT )
Parking and back-up sensor control unit input test (see PARKING AND BACK-UP SENSOR CONTROL UNIT INPUT TEST/REPLACEMENT )
Seat heater control unit input test (see SEAT HEATER CONTROL UNIT INPUT TEST/REPLACEMENT )

Turn the ignition switch to LOCK (0).
Remove the driver's dashboard lower cover (see INSTRUMENT PANEL REMOVAL/INSTALLATION ).
Disconnect under-dash fuse/relay box connector T (34P).
Check for continuity between under-dash fuse/relay box connector T(34P) terminals No. 12 and No. 29.

Fig 1: Checking Continuity Between Under-Dash Fuse/Relay Box Connector T(34P) Terminals No. 12 And 29
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Repair a short in the B-CAN wires.

NO -Go to step 11.
Check for continuity between body ground and under-dash fuse/relay box connector T (34P) terminals No. 12 and No. 29 individually.

Fig 2: Checking Continuity Between Body Ground And Under-Dash Fuse/Relay Box Connector T (34P) Terminals No. 12 And 29
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Repair a short to ground in the B-CAN wire(s).

NO -Go to step 12.
Turn the ignition switch to ON (II).
Measure the voltage between body ground and under-dash fuse/relay box connector T (34P) terminals No. 12 and No. 29 individually.

Fig 3: Measuring Voltage Between Body Ground And Under-Dash Fuse/Relay Box Connector T (34P) Terminals No. 12 And 29
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there voltage?

YES -Repair a short to power in the B-CAN wire(s).

NO -Faulty MICU; replace the under-dash fuse/relay box (see REMOVAL AND INSTALLATION ).