What Does B0507 Mean?
This code indicates the Body Control Module (BCM) has detected a fault in the left-hand (driver side) Daytime Running Lamp relay control circuit. The BCM monitors the relay coil control circuit for opens, shorts to ground, shorts to power, or excessive current draw. This fault prevents proper operation of the left DRL system, which affects vehicle visibility and legal compliance in jurisdictions requiring DRLs.
Common Causes
35%
Failed DRL relay with internal coil open circuit or stuck contacts
30%
Damaged wiring harness or corroded connector at relay socket causing open or short circuit
20%
Blown fuse in DRL circuit or corrosion in fuse holder
10%
BCM internal driver circuit failure preventing proper relay control
5%
Faulty DRL bulbs or socket causing excessive current draw triggering circuit protection
Diagnostic Steps
1
Step 1: Visually inspect the left DRL relay location (typically in power distribution center/fuse box), check for physical damage, overheating marks, corrosion on relay terminals, and verify proper relay seating
2
Step 2: Using a digital multimeter, check for battery voltage at relay socket terminal 85 or 86 (coil power) with ignition on and DRLs commanded active via scan tool bi-directional controls
3
Step 3: Test relay coil resistance (should be 70-120 ohms typically) by removing relay and measuring between coil terminals, then swap relay with known-good identical relay to confirm fault follows component
4
Step 4: Check relay ground circuit at BCM connector with multimeter, verify less than 0.5 ohms resistance to chassis ground, and inspect BCM connector terminals for corrosion, bent pins, or terminal push-back
5
Step 5: If relay and circuits test good, measure current draw of left DRL circuit when activated (should be within specifications, typically under 10 amps for standard bulbs), check for shorts in load side wiring
6
Step 6: Clear codes, operate DRL system through multiple cycles, and monitor live data for relay command status versus actual feedback to confirm repair and verify BCM is properly controlling the circuit
Estimated Repair Cost
$75 - $350
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected a fault in the left-hand (driver side) Daytime Running Lamp relay control circuit. The BCM monitors the relay coil control circuit for opens, shorts to ground, shorts to power, or excessive current draw. This fault prevents proper operat...
The most common cause of B0507 (LH DRL Relay Circuit) is: Failed DRL relay with internal coil open circuit or stuck contacts
Typical repair costs for B0507 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 DRLs are supplemental lighting and do not affect primary headlamps or brake lights. However, reduced daytime visibility to other drivers increases minor collision risk, and driving may be illegal in jurisdictions with mandatory DRL laws.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B0507 to identify the root cause.
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Quick Info
Category
Body
System
Exterior Lighting System
Difficulty
Type
Generic (SAE)
Recommended Tools
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