What does it mean?
B1835 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Driver Seat Lumbar Rearward Switch Circuit .
Symptoms
- Lumbar support will not retract, while the forward direction still works
- Lumbar moves in one direction only and has to be reset manually
- No motor or pump sound when the rearward direction is selected
- Memory recall skips the lumbar position while the rest of the seat moves
- Lumbar adjusts on its own without the switch being touched
Likely causes
- Worn or dirty contacts in the lumbar switch on the seat side trim
- Open or short circuit in the lumbar rearward signal wire
- Under-seat harness pinched by the seat rails at full travel
- Liquid spilled down the side of the seat into the switch housing
- Loose or corroded under-seat connector after seat removal or interior cleaning
- Weak power supply or ground at the seat control module
- Module input stage failure
How to fix it
- Operate the lumbar switch while watching its status in live data
- Unplug the switch and measure the contact resistance at rest and pressed
- Back-probe the module input pin and look for the expected voltage change
- Move the seat through its full travel and inspect the harness for pinching
- Check the seat module fuse, supply and ground with a voltage drop test
- Replace the switch assembly if the contacts are open or erratic
- Replace the seat module last and relearn the memory positions