What Does B1807 Mean?
B1807 indicates the Body Control Module (BCM) has detected an open circuit in the tail lamp output circuit. This means the BCM is commanding the tail lamps to illuminate, but electrical continuity is broken somewhere between the BCM output driver and the tail lamp bulbs/LEDs. The open circuit prevents current flow, resulting in non-functional tail lamps on one or both sides of the vehicle.
Common Causes
40%
Failed tail lamp bulb(s) or corroded bulb socket contacts creating open circuit
30%
Broken or damaged wiring between BCM and tail lamp assembly, often in trunk hinge area or rear harness
20%
Corroded or loose connector at tail lamp assembly or BCM connector terminals
10%
Failed BCM output driver transistor for tail lamp circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of tail lamp bulbs and sockets. Remove bulbs and inspect for blown filaments, corrosion, or damaged socket terminals. Check for proper bulb contact and ground connection at socket.
2
Step 2: Using a digital multimeter, check for battery voltage at the tail lamp connector with parking lamps commanded ON. Backprobe the power wire at the lamp connector. No voltage indicates wiring or BCM issue; voltage present indicates bulb/socket/ground problem.
3
Step 3: Inspect tail lamp wiring harness from BCM to lamp assembly, paying close attention to flex points (trunk hinge, door jambs, body seams). Look for chafed, pinched, or broken wires. Check all connectors for corrosion, bent pins, or water intrusion.
4
Step 4: Test circuit continuity with multimeter in ohms mode. Disconnect BCM connector and tail lamp connector, measure resistance between BCM tail lamp output pin and lamp connector power pin. Should read less than 5 ohms; infinite resistance confirms open circuit in wiring.
5
Step 5: If wiring and connections test good, monitor BCM output command with scan tool bi-directional controls. Command tail lamps ON/OFF while measuring voltage at BCM connector pin. If BCM provides proper voltage output, recheck wiring; if no output, BCM driver circuit is failed.
6
Step 6: After repairs, clear codes, cycle tail lamps multiple times, and verify proper operation. Road test vehicle and confirm DTC does not return.
Estimated Repair Cost
$50 - $450
Parts + labor, varies by vehicle and location
B1807 indicates the Body Control Module (BCM) has detected an open circuit in the tail lamp output circuit. This means the BCM is commanding the tail lamps to illuminate, but electrical continuity is broken somewhere between the BCM output driver and the tail lamp bulbs/LEDs. The open circuit preven...
The most common cause of B1807 (Lamp Tail Output Circuit Open) is: Failed tail lamp bulb(s) or corroded bulb socket contacts creating open circuit
Typical repair costs for B1807 range from $50 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is not safe to drive after dark or in poor visibility conditions as non-functional tail lamps make the vehicle nearly invisible to following traffic, creating serious rear-end collision risk. Repair immediately before operating vehicle at night or obtain temporary lighting solution.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1807 to identify the root cause.
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Quick Info
Category
Body
System
Exterior Lighting System
Difficulty
Type
Manufacturer
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