DTC B1843: UART Communication Error

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2015 Honda Crosstour, 2014 Honda Crosstour, 2013 Honda Crosstour, 2012 Honda Crosstour, and 2011 Honda Accord Crosstour. However, it is still accessible from the selected car via links, so may be relevant.

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).
Operate the power seat with the driving position memory switch.
Check for DTCs with the HDS.
Is DTC B1843 indicated?

YES -Go to next step.

NO -Intermittent failure, the system is OK at this time. Check for loose or poor connections.
Turn the ignition switch to LOCK (0).
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. 23 and power mirror control unit (24P) connector terminal No. 24.

Fig 1: Checking Continuity Between Power Seat Control Unit Connector B (40P) Terminal No. 23 And Power Mirror Control Unit Connector (24P) Terminal No. 24
Courtesy of ABLE BODY CORP.

Is there continuity?

YES -Go to next step.

NO -Repair an open in the UART 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. 23.

Fig 2: Checking Continuity Between Body Ground And Power Seat Control Unit Connector B (40P) Terminal No. 23
Courtesy of ABLE BODY CORP.

Is there continuity?

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

NO -Go to next step.
Reconnect the power mirror control unit (24P) connector.
Measure the voltage between body ground and power mirror control unit connector (24P) terminal No. 13.

Fig 3: Measuring Voltage Between Body Ground And Power Mirror Control Unit Connector (24P) Terminal No. 13
Courtesy of ABLE BODY CORP.

Is there battery voltage?

YES -Go to next step.

NO -Check No. A15 (10 A) fuse in the under-hood fuse/relay box. If the fuse is OK, repair an open or high resistance in the wire.
Turn the ignition switch to ON (II).
Measure the voltage between body ground and power mirror control unit connector (24P) terminal No. 15.

Fig 4: Measuring Voltage Between Body Ground And Power Mirror Control Unit Connector (24P) Terminal No. 15
Courtesy of ABLE BODY CORP.

Is there 0.2 V or more?

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.