What does it mean?
B2161 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Driver's MPCS Unit Lost Communication with MICU (DOORSW Message .
Symptoms
- Seat front height cannot be stored in memory, or the stored value is ignored
- Memory recall raises the seat to the wrong height or stops partway
- Front of the cushion moves in one direction only
- Motor runs but the position value in live data does not change
- Memory works for mirrors and column but not for the seat height
- Code returns each time a memory recall is attempted
Likely causes
- Position sensor in the front vertical motor worn, dirty or failed
- Front lift mechanism binding, so the motor stalls before the stored position is reached
- Stored values corrupted after a battery disconnection or a low voltage event
- Seat calibration never performed after a motor, seat or module was replaced
- Under seat harness stretched or broken by the seat sliding through its travel
- Connector under the seat loose or corroded
- Weak battery causing the motor to slow and the module to miscount pulses
- Memory module internal fault, considered last
How to fix it
- Confirm the manufacturer definition and the pin assignment for the front vertical motor
- Test the battery and charging system, memory seat faults often follow a weak battery
- Watch the front vertical position value in live data through the full travel
- Move the seat manually with the motor unplugged to check the mechanism is free
- Inspect and flex the under seat harness while watching live data
- Reseat the under seat connectors and check for corrosion
- Perform the seat position relearn or calibration procedure specified for the vehicle
- If the position value still does not track the movement, replace the motor and sensor assembly, then recalibrate and verify each memory setting