DTC B1843: UART Communication Error

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), or press the engine start/stop button to select the OFF mode and then the ON mode.
Operate the power seat with the driving position memory switch.
Check for DTCs with the HDS.
Is DTC B1843 Indicated?

YES -Go to step 5.

NO -Intermittent failure, the system is OK at this time. Check for loose or poor connections.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.
Disconnect these items:
- Power seat control unit connector A (18P)
- Power seat control unit connector B (40P)
- Power mirror control unit 24P connector
Check for continuity between power seat control unit connector B (40P) terminal No. 38 and power mirror control unit 24P connector terminal No. 13.

Fig 1: Checking Continuity Between Power Seat Control Unit Connector B (40P) Terminal 38 And Power Mirror Control Unit 24P Connector Terminal 13
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 8.

NO -Repair an open in the UART wire between the power mirror control unit and the power seat control unit.
Disconnect the power tilt/telescopic steering control unit connectors.
Check for continuity between body ground and power seat control unit connector B (40P) terminal No. 38.

Fig 2: Checking Continuity Between Body Ground And Power Seat Control Unit Connector B (40P) Terminal 38
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Repair a short to ground in the UART wire.

NO -Go to step 10.
Reconnect the power mirror control unit 24P connector.
Measure the voltage between body ground and power mirror control unit 24P connector terminal No. 24.

Fig 3: Measuring Voltage Between Body Ground And Power Mirror Control Unit 24P Connector Terminal 24
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Go to step 12.

NO -Check No. 15 (10 A) fuse in the under-hood fuse/relay box. If the fuse is OK, repair an open or high resistance in the wire.
Check for continuity between body ground and power mirror control unit 24P connector terminal No. 22.

Fig 4: Checking Continuity Between Body Ground And Power Mirror Control Unit 24P Connector Terminal 22
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Replace the power mirror control unit (see POWER MIRROR CONTROL UNIT INPUT TEST/REPLACEMENT ).

NO -Repair an open or high resistance in the wire between the power mirror control unit and body ground (G402). If the wire is OK, repair the body ground (G402).