What does it mean?
B1279 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Headlight Switch DIMMER Position Circuit Malfunction .
Symptoms
- High beams cannot be selected, or stay on and cannot be switched back to low beam
- The headlamp flash (passing) function does not work
- The high beam indicator in the cluster does not match the actual lamps
- Beam selection works only intermittently, or only while the stalk is held in position
- Automatic high beam control, where fitted, stops working
Likely causes
- Worn or burnt dimmer contacts inside the combination light switch stalk
- Open or shorted wiring between the dimmer position terminal and the body control module
- Corroded or loose connector at the steering column
- Moisture or spilled liquid inside the switch assembly
- Harness damage under the column from previous clockspring or airbag service
- Failed input circuit inside the body control module
How to fix it
- Operate the stalk through low beam, high beam, and flash and note exactly which functions fail
- Watch the dimmer switch status in live data while moving the stalk
- Disconnect the combination switch and check continuity of the dimmer contacts in each position
- Inspect the connector for corrosion, burnt terminals, and moisture
- Test the dimmer wire between the switch and the body control module for opens and shorts
- Replace the combination switch if its contacts are worn, then verify low beam, high beam, flash, and the cluster indicator