B2509
Low Severity (Level 2)Rear Fog Lamp Switch Circuit Failure
B2509 usually means rear Fog Lamp Switch Circuit Failure.
Can you still drive with B2509?
⚠️Short-distance driving is usually OK, but have this diagnosed within a week to prevent further damage.
Typical repair cost: $50 – $600
Severity Level 2 — Low
This code indicates a minor issue that is unlikely to cause immediate driveability problems. You can typically continue driving but should have the vehicle inspected at your earliest convenience.
Common Symptoms
- Body electronics not functioning as expected
- Warning light or message on dashboard related to the body control/comfort system
- Diagnostic trouble code (DTC) stored in module memory
- Fault may be intermittent — code may clear itself and reappear
- Reduced vehicle functionality related to the body control/comfort system
Possible Causes
- Failed body control module or actuator — internal fault from age, heat cycling, and vibration
- Damaged wiring or corroded connector in the body control/comfort system circuit
- Blown fuse for the body control/comfort system circuit — check before replacing components
- Faulty control module/PCM
- Loose or corroded ground point shared by the body control/comfort system
Common Fixes
- Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($14-119 at shop, free at auto parts store for basic scan)
- Visually inspect the body control/comfort system wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $120 diagnostic fee at shop)
- Replace body control module or actuator if testing confirms it has failed — use OEM quality, avoid the cheapest no-name aftermarket parts that fail in a year ($50-600)
- Check and replace any blown fuses in the body control/comfort system fuse circuit — if fuse blows again, there's still a short that needs to be found ($4-20 for fuses)
- Perform a wiggle test on the body control/comfort system wiring harness while monitoring live data — see if the fault returns when you move the harness at different points ($0-107 diagnostic labor)
Estimated Repair Cost
These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.
Frequently Asked Questions
What does B2509 mean?
B2509 stands for "Rear Fog Lamp Switch Circuit Failure". B2509 usually means rear Fog Lamp Switch Circuit Failure.
Can you drive with B2509?
Short-distance driving is usually OK, but have this diagnosed within a week to prevent further damage.
How much does it cost to fix B2509?
Repair costs for B2509 typically range from $50 to $600, depending on your vehicle make, model, and local labor rates. Common fixes include: Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($14-119 at shop, free at auto parts store for basic scan); Visually inspect the body control/comfort system wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $120 diagnostic fee at shop); Replace body control module or actuator if testing confirms it has failed — use OEM quality, avoid the cheapest no-name aftermarket parts that fail in a year ($50-600).
Will B2509 clear itself?
Explore Repair Costs
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