B0820 code meaning
Left Headlamp High Beam Circuit
What B0820 means
B0820 is undocumented: neither open J2012 material nor factory or NHTSA papers list it. The title refers to the left main-beam output. In the second-generation Saab 9-3 the front electrical centre flags B2580 04 when the left main beam draws under 0.8 A while switched on and B2580 0B for 7.9 to 30 A. GM's 2011 Saab 9-5 works differently: both main beams are fed through one relay whose coil the body control module grounds, and if that control line is shorted to battery plus, B2580 01 is stored with both high beams off. HELLA points out that bi-xenon units form low and high beam in one module by moving a shutter, so a fault can also sit in that mechanism. FMVSS 108 requires an upper-beam indicator for the driver. Right side: B0821.
B0820 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.2 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of B0820
- Left main beam stays dark when high beam is selected
- Both main beams fail if the shared relay circuit is affected
- Lamp failure message in the display
Common causes of B0820
- Most likelyLeft high-beam bulb burnt out
- PossibleHigh-beam relay or its control line faulty
- PossibleShutter actuator in a bi-xenon module stuck
- Less likelyCorroded headlamp connector
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Left high beam lampBody control module
What each part of B0820 means
| B | Body system: airbags, seat belts, power seats, lights and climate control. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 20 | The exact fault in that area. |
What to do next
- Note B0820 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about B0820
What does B0820 mean?
B0820 means "Left Headlamp High Beam Circuit". B0820 is undocumented: neither open J2012 material nor factory or NHTSA papers list it. It is a generic code, so it means the same on every make.
Is it safe to drive with B0820?
B0820 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B0820 fail an emissions test?
B0820 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is B0820 to fix?
Difficulty: easy. A typical repair takes 0.2 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will B0820 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.