What Does B2408 Mean?
DTC B2408 indicates the Body Control Module (BCM) has detected an electrical fault in the rear fog lamp switch circuit. This occurs when the BCM monitors abnormal voltage, resistance, or signal behavior from the rear fog lamp switch that falls outside expected parameters. The fault may present as an open circuit, short to ground, short to power, or excessive resistance in the switch or its associated wiring.
Common Causes
45%
Faulty rear fog lamp switch with internal contact failure or wear
30%
Damaged wiring harness or corroded connector between BCM and rear fog lamp switch
15%
Poor ground connection or open ground circuit at switch or lamp assembly
10%
Body Control Module internal circuit fault or software corruption
Diagnostic Steps
1
Step 1: Perform visual inspection of the rear fog lamp switch, connector, and wiring harness for obvious damage, corrosion, moisture intrusion, or loose connections. Wiggle the switch and connectors while observing for intermittent fault behavior.
2
Step 2: Using a digital multimeter, check voltage supply at the rear fog lamp switch connector with ignition on. Verify presence of battery voltage (typically 12-14V) on supply wire according to wiring diagram for your specific vehicle.
3
Step 3: Test switch operation by measuring continuity across switch terminals in both ON and OFF positions. Switch should show continuity (less than 5 ohms) when activated and infinite resistance when off. Replace switch if readings are incorrect.
4
Step 4: Verify ground circuit integrity by measuring resistance between switch ground terminal and known good chassis ground. Reading should be less than 1 ohm. Repair or clean ground connections if resistance is excessive.
5
Step 5: Check wiring harness continuity between BCM connector and switch connector for each circuit wire. Look for opens (infinite resistance) or shorts to ground/power (unexpected continuity). Repair wiring as needed.
6
Step 6: Clear codes, cycle rear fog lamp switch through all positions multiple times, and verify repair by monitoring live data for proper switch status signal at BCM. Test drive and recheck for code return.
Estimated Repair Cost
$75 - $350
Parts + labor, varies by vehicle and location
DTC B2408 indicates the Body Control Module (BCM) has detected an electrical fault in the rear fog lamp switch circuit. This occurs when the BCM monitors abnormal voltage, resistance, or signal behavior from the rear fog lamp switch that falls outside expected parameters. The fault may present as an...
The most common cause of B2408 (Rear Fog Lamp Switch Circuit) is: Faulty rear fog lamp switch with internal contact failure or wear
Typical repair costs for B2408 range from $75 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as rear fog lamps are supplementary lighting and not required for basic vehicle operation in most jurisdictions. Repair at earliest convenience to maintain full lighting functionality and visibility in adverse weather conditions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2408 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Body
System
Body Electrical System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
