What Does B1504 Mean?
This code indicates the Body Control Module (BCM) has detected an open circuit in the right turn signal lamp circuit. An open circuit means there is a break in the electrical pathway preventing current flow to the right turn signal bulb(s). The BCM monitors the circuit and sets this code when it cannot detect proper current flow or voltage feedback from the lamp circuit.
Common Causes
45%
Burned out or missing right turn signal bulb causing open circuit
30%
Corroded or damaged bulb socket with poor electrical connection
15%
Broken or severed wire in right turn signal circuit harness
10%
Failed BCM output driver or internal relay for turn signal circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of right turn signal lamp assembly - check if bulb is present, intact, and properly seated in socket. Remove bulb and inspect for broken filament or base damage.
2
Step 2: Inspect bulb socket for corrosion, burned terminals, melted plastic, or damage. Clean terminals with electrical contact cleaner and wire brush if corrosion is present. Check socket ground connection.
3
Step 3: Using a digital multimeter, check for voltage at the bulb socket with turn signal activated (should read 12V+ on signal wire). If no voltage, backprobe connector closer to BCM to isolate wire break location.
4
Step 4: Check continuity of the circuit from bulb socket back to BCM connector with multimeter in ohms mode (key off, harness disconnected). Reading should be less than 5 ohms; infinite resistance confirms open circuit.
5
Step 5: If wiring and socket test good, verify ground circuit integrity with multimeter from socket ground to chassis ground (should be less than 1 ohm resistance).
6
Step 6: After repairs, install known-good bulb, clear code, and activate turn signals multiple times to verify proper operation and confirm code does not return.
Estimated Repair Cost
$50 - $300
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an open circuit in the right turn signal lamp circuit. An open circuit means there is a break in the electrical pathway preventing current flow to the right turn signal bulb(s). The BCM monitors the circuit and sets this code when it can...
The most common cause of B1504 (Lamp Turn Signal Right Circuit Open) is: Burned out or missing right turn signal bulb causing open circuit
Typical repair costs for B1504 range from $50 to $300, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Not safe to drive without functioning turn signals as it violates traffic laws and creates serious safety hazard by preventing communication of intended direction changes to other drivers. Repair should be completed before operating vehicle on public roads.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1504 to identify the root cause.
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Quick Info
Category
Body
System
Exterior Lighting System
Difficulty
Type
Manufacturer
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