DTC B2187: Communication Line (UART Line) Circuit Short

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 OFF, and then back ON (II).
Operate the front passenger's, left rear and right rear power window switches.
Check for DTCs with the HDS.
Is DTC B2187 indicated?

YES - Go to step 5.

NO - Intermittent failure, the UART line is OK at this time.
Turn the ignition switch OFF.
Disconnect these connectors:
- Driver's MPCS unit connector A (40P)
- Power window master switch 6P connector
- Front passenger's MPCS unit connector A (28P)
- Left rear power window switch 14P connector
- Right rear power window switch 14P connector
- Moonroof motor/control unit 8P connector
Check for continuity between driver's MPCS unit connector A (40P) terminal No. 8 and body ground.

Fig 1: Checking Continuity Between Driver's MPCS Unit Connector A (40P) Terminal No. 8 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES - Repair a short to ground in the wire.

NO - Go to step 8.
Turn the ignition switch ON (II).
Measure the voltage between driver's MPCS unit connector A (40P) terminal No. 8 and body ground.

Fig 2: Measuring Voltage Between Driver's MPCS Unit Connector A (40P) Terminal No. 8 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there voltage?

YES - Repair a short to power in the wire.

NO - Go to step 10.
Clear the DTCs with the HDS.
Turn the ignition switch OFF, and then back ON (II).
Wait for 6 seconds or more.
Check for DTCs with the HDS.
Is DTC B2187 indicated?

YES - Replace the driver's MPCS unit.

NO - Go to step 14.
Reconnect the power window master switch 6P connector.
Clear the DTCs with the HDS.
Turn the ignition switch OFF, and then back ON (II).
Operate each switch of the power window master switch.
Check for DTCs with the HDS.
Is DTC B2187 indicated?

YES - Replace the power window master switch.

NO - Go to step 19.
Reconnect front passenger's MPCS unit connector A (28P).
Clear the DTCs with the HDS.
Turn the ignition switch OFF, and then back ON (II).
Operate the front passenger's power window switch in each direction.
Check for DTCs with the HDS.
Is DTC B2187 indicated?

YES - Replace the front passenger's MPCS unit.

NO - Go to step 24.
Reconnect the right rear power window switch 14P connector.
Clear the DTCs with the HDS.
Turn the ignition switch OFF, and then back ON (II).
Operate the right rear power window switch in each direction.
Check for DTCs with the HDS.
Is DTC B2187 indicated?

YES - Replace the right rear power window switch.

NO - Go to step 29.
Reconnect the left rear power window switch 14P connector.
Clear the DTCs with the HDS.
Turn the ignition switch OFF, and then back ON (II).
Operate the left rear power window switch in each direction.
Check for DTCs with the HDS.
Is DTC B2187 indicated?

YES - Replace the left rear power window switch.

NO - Go to step 34.
Reconnect the moonroof motor/control unit 8P connector.
Clear the DTCs with the HDS.
Turn the ignition switch OFF, and then back ON (II).
Open and close the moonroof with the moonroof switch.
Check for DTCs with the HDS.
Is DTC B2187 indicated?

YES - Replace the moonroof motor/control unit.

NO - Replace the driver's MPCS unit.