Fog Light Control Circuit Malfunction
The B0079 code means the vehicle's onboard diagnostic system has detected: Fog Light Control Circuit Malfunction. This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $20 - $250 (parts and labor)
Basic scanners skip body codes entirely. BlueDriver reads airbag, HVAC, lighting, and BCM codes through your phone.
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Common Symptoms
- Neither fog light illuminates
- Fog switch does not activate lights
- Fog indicator not working
- Fog lights intermittent
Probable Causes (Ranked by Likelihood)
- Failed fog light relay Very High
- Faulty fog light switch High
- Blown fog light fuse Moderate
- BCM fog light output failure Low
Step-by-Step Diagnostic Procedure
-
Check fog light fuse
-
Swap relay with identical one
-
Test switch continuity
-
Scan BCM for fog codes
Frequently Asked Questions
Can a blown fuse cause both to fail?
Yes, both share a single fuse and relay.
How do I test the relay?
Swap with another identical relay in the fuse box.
Why only work sometimes?
Intermittent operation indicates a loose or corroded connection.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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