B0850Left Brake Lamp Circuit
- Generic OBD-II code · Body
- How the car detects it
- B0850 cannot be confirmed from any open source – J2012 tables, OEM documentation and NHTSA bulletins omit it. The title covers the left stop lamp. In Saab's 9-3 (type 9440) the rear electrical centre checks it while braking under its own number B3445: below 50 mA it records an open circuit (04), and once current tops 6 A for over 6 ms a short to ground (02), shutting the output down. The third, high-level brake light is logged separately there (B3884). FMVSS 108 makes stop lamps mandatory and defines the high-mounted lamp as a steady stop warning visible through other vehicles. HELLA lists bulbs, holders, fuses and plug connections as the first checks. A missing brake light weakens the warning to following drivers and should be repaired at once. Right side: B0851.
- What you may notice
- Left brake light stays dark when braking, warning shown
- Weaker warning to following traffic; repair before further driving
- Tail light on the same side may also be affected with combined bulbs
- Likely causes
- LikelyLeft stop-lamp bulb or filament failed
- PossibleCorroded bulb holder in the tail lamp
- PossibleOpen or grounded wire to the left tail lamp
- RareStop-lamp output of the rear module faulty
- Repair
- Easy · Often possible to do yourself.Typical cost: €5 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.