What does it mean?
B1846 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Power Seat Front Up-Down Switch Circuit Malfunction .
Symptoms
- Front edge of the seat cushion will not raise or lower while the rest of the seat works
- Cushion tilt moves in one direction only, leaving the seat at an angle
- Cushion tilt moves without the switch being pressed
- Memory recall leaves the cushion angle wrong
- No motor noise from the front lift motor
Likely causes
- Front height switch contacts worn or dirty inside the seat switch pack
- Open or short circuit in the front up-down signal wire
- Under-seat harness pinched between the seat frame and the rail
- Liquid or dirt inside the switch housing on the seat side trim
- Corroded or loose under-seat connector
- Front lift motor binding and drawing high current
- Seat module input stage failure
How to fix it
- Operate the front up-down switch while watching its status in live data
- Unplug the switch pack and measure the contacts in both actuated directions
- Inspect the harness under the cushion with the seat raised and lowered fully
- Back-probe the module input pin and look for the voltage change
- Measure the front lift motor current to see whether the mechanism is binding
- Replace the switch pack if the contacts are open or erratic
- Replace the seat module last and recalibrate the memory positions