B0800 code meaning
Headlamp Switch Circuit
What B0800 means
B0800 lacks any public evidence; no J2012 extract or service document mentions it. The title concerns the light switch that tells the body control module which lamps to energise. In the GM-developed Saab 9-3 the BCM checks switch positions 1 and 2 and logs B2585 05 or B2575 05 when the respective line rises above 10.2 V; dipped beam then stays on whatever the switch says. GM's 2011 Saab 9-5 compares its headlamp-on and headlamp-off inputs, stores B257A on an implausible combination and falls back to automatic headlamp control. FMVSS 108 requires every car to have a dipper switch and a high-beam telltale. Both fallbacks keep the lights usable, so the fault mostly shows as lost manual control rather than darkness.
B0800 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of B0800
- Dipped beam stays on regardless of switch position
- Lights only work in automatic mode
- Parking lights cannot be selected separately
Common causes of B0800
- Most likelyWorn or corroded contacts in the light switch
- PossibleSwitch signal wire shorted to battery voltage
- PossibleLoose or damaged plug behind the switch
- Less likelySwitch input of the body control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Headlamp switchBody control module
What each part of B0800 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). |
| 00 | The exact fault in that area. |
What to do next
- Note B0800 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 B0800
What does B0800 mean?
B0800 means "Headlamp Switch Circuit". B0800 lacks any public evidence; no J2012 extract or service document mentions it. It is a generic code, so it means the same on every make.
Is it safe to drive with B0800?
B0800 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B0800 fail an emissions test?
B0800 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 B0800 to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will B0800 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.