B0840Left Rear Turn Signal Circuit
- Generic OBD-II code · Body
- How the car detects it
- Neither J2012 extracts nor any OEM or NHTSA publication name B0840; its use is unproven. The title concerns the left rear indicator. In the 2003–2012 Saab 9-3 the rear electrical centre supervises this lamp under the number B0530: an open lamp (04) or a short to ground (02) shows up as a warning message and the remaining indicators flashing at double speed, which is exactly the pilot-indicator behaviour FMVSS 108 permits for a failed turn lamp. HELLA notes that modern rear lamps are driven by body or lighting control units and may consist of LED segments, so diagnosis should include fault codes, connectors and the supply to the lamp unit. A failed rear indicator hides lane changes from following traffic. Right rear: B0841.
- What you may notice
- Indicators flash at double speed when signalling left
- Left rear indicator dark, warning message shown
- Lane changes not visible to following traffic; repair promptly
- Likely causes
- LikelyRear indicator bulb or LED segment failed
- PossibleCorroded plug or bulb carrier in the rear lamp
- PossibleWire break in the boot lid or tailgate harness
- RareRear electrical centre output faulty
- Repair
- Easy · Often possible to do yourself.Typical cost: €5 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.