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 DTC 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
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode
Disconnect the power seat control unit connectors and power mirror control unit connector (24P)
Check for continuity between power seat control unit connector B (40P) terminal No 38 and power mirror control unit connector (24P) terminal No 13

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

Is there continuity?

YES -Go to step 8

NO -Repair open in the wire between the power mirror control unit connector (24P) and power seat control unit connector B (40P)
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 short to ground in the wire

NO -Go to step 9
Disconnect the power seat control unit connectors (24P)
Measure the voltage between body ground and power mirror control unit connector (24P) terminal No 24

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

Is there battery voltage?

YES -Go to step 11

NO -Check No 15 (10 A) fuse in the under-hood fuse/relay box If the fuse is OK, repair open in the wire
Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.
Measure the voltage between body ground and power mirror control unit connector (24P) terminal No. 22.

Fig 4: Measuring voltage between body ground and power mirror control unit connector (24P) terminal No. 22
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there less than 0.2 V?

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 G401. If the wire is OK, repair G401.