Left Rear Fog Light Circuit Malfunction
The B0090 code means the vehicle's onboard diagnostic system has detected: Left Rear Fog Light Circuit Malfunction. This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- easy
- Estimated cost
- $10 - $150 (parts and labor)
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Common Symptoms
- Left rear fog light not illuminating
- Rear fog indicator on but light not working
- Reduced rear fog visibility
- Failed rear fog light inspection
Probable Causes (Ranked by Likelihood)
- Burned out rear fog light bulb Very High
- Corroded rear fog socket High
- Damaged wiring to rear fog Moderate
- Rear fog relay failure Low
Step-by-Step Diagnostic Procedure
-
Inspect rear fog bulb
-
Check socket for corrosion
-
Test voltage at connector
-
Check relay and fuse
Frequently Asked Questions
Do all vehicles have rear fog lights?
Required in Europe; most US and Japanese vehicles do not.
Is it different from the brake light?
Yes, a separate high-intensity red light for fog visibility.
Why only one rear fog?
To prevent confusion with brake lights.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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