DTC B1843: Power Seat Control Unit Lost Communication with Power Tilt/Telescopic Steering Control Unit (UART line)

WARNING: This page is about a different car, the 2013 Acura MDX, 2012 Acura MDX, 2011 Acura MDX, and 2010 Acura MDX. 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 DTCs with the HDS.
Turn the ignition switch to LOCK (0) and then back to ON (II).
Check for DTCs with the HDS.
Is DTC B1843 indicated?

YES -Go to step 4.

NO -Intermittent failure, the system is OK at this time. Check for loose or poor connections.
Move the power tilt/telescopic steering in each direction with the power tilt/telescopic steering switch.
Does the tilt/telescopic steering move in each direction smoothly?

YES -Go to step 5.

NO -Go to step 10.
Turn the ignition switch to LOCK (0).
Disconnect power seat control unit connector A (40P).
Disconnect power tilt/telescopic steering control unit connector A (16P).
Check for continuity between power seat control unit connector A (40P) terminal No. 39 and power tilt/telescopic steering control unit connector A (16P) terminal No. 11.

Fig 1: Checking Continuity Between Connector (40P) Terminal And Connector (16P) Terminal No. 11
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 9.

NO -Repair an open in the wire.
Check for continuity between power seat control unit connector A (40P) terminal No. 39 and body ground.

Fig 2: Checking Continuity Between Connector (40P) Terminal No. 39 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Repair a short to ground in the wire.

NO -Substitute a known-good power tilt/telescopic steering control unit and recheck. If DTC B1843 is still indicated, replace the power seat control unit.
Turn the ignition switch to LOCK (0).
Disconnect power tilt/telescopic steering control unit connectors A (16P) and B (8P).
Turn the ignition switch to ON (II).
Measure the voltage between power tilt/telescopic steering control unit connector A (16P) terminal No. 9 and connector B (8P) terminal No. 1, and between connector A (16P) terminal No. 1 and connector B (8P) terminal No. 1.

Fig 3: Measuring Voltage Between Connector A (16P) And Connector B (8P)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Replace the power tilt/telescopic steering control unit.

NO -Do the power tilt/telescopic steering control unit input test (see POWER TILT/TELESCOPIC STEERING CONTROL UNIT INPUT TEST ).