What does it mean?
B2187 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Communication Line (UART Line) Driver's MPCS Unit cannot send UART messages. .
Symptoms
- Rear wiper stuck on, or dead, depending on which definition applies
- Memory seat, mirror and column functions completely inoperative
- Seat still moves on the manual switches but nothing is stored or recalled
- Scan tool cannot communicate with the seat control unit
- Warning message about a system fault in the display
- Several related communication codes stored in other modules
Likely causes
- Rear wiper switch contacts stuck closed or bridged by moisture
- Broken wiring in the tailgate boot or a corroded tailgate connector
- Serial communication wire between the seat control unit and the other body modules open or shorted
- Connector under the driver seat loose, damp or corroded
- Poor ground for the seat control unit, which stops it driving the communication line properly
- Low system voltage while several motors are running
- Water damage under the carpet reaching the module or its connector
- Seat control unit internal fault, which stops it transmitting at all
How to fix it
- Look up the manufacturer definition, the two possible meanings need completely different work
- For the wiper variant, unplug the rear wiper switch and check the input for a short to ground, then inspect the tailgate boot loom
- For the communication variant, check power, ground and fuses at the seat control unit first
- Lift the carpet under the seat and look for damp, corrosion and a damaged loom
- Measure the communication line for continuity, and for shorts to ground and to battery, with the module unplugged
- Confirm the battery and charging system are healthy before condemning any module
- Repair the harness or connector, or replace the faulty unit if it has good supplies and still cannot transmit
- Clear the codes, then verify both the wiper function and the memory functions operate correctly