What Does B2566 Mean?
This code indicates the Body Control Module (BCM) has detected an abnormal low resistance or direct ground path in the right tail lamp circuit. The BCM monitors the lamp circuit and sets this code when current flow exceeds normal parameters due to a short to ground condition. This prevents proper tail lamp operation and may cause fuse failure or BCM damage if not corrected.
Common Causes
40%
Damaged or chafed wiring harness creating a ground short, typically at pinch points, body panels, or suspension mounting areas
30%
Corroded or water-damaged tail lamp socket with internal short circuit to ground
15%
Failed tail lamp bulb with internal filament-to-base short circuit
10%
Moisture intrusion or corrosion in BCM connector terminals causing internal short
5%
Aftermarket trailer wiring or accessory installation creating inadvertent ground path
Diagnostic Steps
1
Step 1: Perform visual inspection of right tail lamp assembly for water intrusion, cracked lens, corroded socket, or damaged wiring. Remove bulb and inspect for blackened base or bent contacts indicating short circuit.
2
Step 2: Disconnect right tail lamp connector at lamp housing. Use multimeter to measure resistance from lamp circuit wire (typically brown or red wire at connector) to chassis ground. Reading should be infinite ohms (open circuit); any continuity indicates short to ground downstream of connector.
3
Step 3: If Step 2 shows open circuit, reconnect lamp connector and disconnect BCM connector. Measure resistance from tail lamp circuit pin at BCM to chassis ground. Infinite resistance confirms wiring harness is intact; continuity indicates short between BCM and lamp.
4
Step 4: Perform wiggle test on suspect wiring harness sections while monitoring resistance, focusing on areas near body seams, door hinges, trunk lid, and rear suspension mounting points to isolate intermittent shorts.
5
Step 5: If no wiring faults found, inspect BCM connectors for corrosion, pushed-back pins, or moisture. Check for aftermarket wiring splices or trailer harness connections that may be incorrectly installed.
6
Step 6: After repairs, clear codes and cycle tail lamps on/off multiple times. Verify BCM no longer detects short circuit and tail lamp operates normally. Perform road test with all lighting functions active to confirm repair.
Estimated Repair Cost
$75 - $400
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an abnormal low resistance or direct ground path in the right tail lamp circuit. The BCM monitors the lamp circuit and sets this code when current flow exceeds normal parameters due to a short to ground condition. This prevents proper ta...
The most common cause of B2566 (Right Tail Lamp Circuit Short to Ground) is: Damaged or chafed wiring harness creating a ground short, typically at pinch points, body panels, or suspension mounting areas
Typical repair costs for B2566 range from $75 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is drivable but rear visibility to other drivers is compromised, creating collision risk especially at night or in poor weather. Repair should be completed within 24-48 hours to maintain legal compliance and traffic safety.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2566 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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