What does it mean?
B1637 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Right High Beam Control Circuit Low .
Symptoms
- Right high beam does not light while the left main beam works
- Lighting fuse blows, or the output disables itself shortly after the high beams are selected
- In some short patterns the right high beam glows faintly or stays on with the lamps off
- Warning message about a lamp failure on the right side
- The overtaking flash function does not work on that side
Likely causes
- Short to ground in the right high beam control wire, often at a chafe point near the battery tray or the front support
- Corrosion or moisture bridging the terminals inside the right headlamp connector
- Bulb with a higher wattage than specified, or auxiliary lamps tapped into the high beam circuit
- Damaged or deformed bulb socket allowing a terminal to touch the housing
- Harness pinched during front end or headlamp replacement work
- Shorted high beam driver inside the lighting control module
How to fix it
- Unplug the right headlamp connector and see whether the code still sets; if it does, the fault is in the wiring or the module
- Examine the connector and socket for burnt or melted terminals and for water inside the housing
- Measure the resistance from the control wire to ground with the connector disconnected; a very low value confirms a short to ground
- Wiggle the harness section by section while watching the meter, concentrating on brackets and body edges the loom passes
- Remove any accessory lighting connected to this circuit and refit the correct bulb type
- Repair the harness with sealed connections rather than tape, then test the high beams repeatedly and clear the code
- Replace the module only when the wiring is proven clean and the output is still faulty