What Does B1503 Mean?
This code indicates the Body Control Module (BCM) has detected an electrical fault in the right turn signal lamp circuit. The BCM monitors current flow and has identified either an open circuit, short circuit, excessive resistance, or bulb failure in the right turn signal lighting system. This is a manufacturer-specific body code related to exterior lighting control and communication.
Common Causes
45%
Burned out turn signal bulb or poor bulb socket connection with corrosion
30%
Damaged or corroded wiring harness between BCM and right turn signal assembly
15%
Faulty turn signal assembly with internal circuit board failure or moisture intrusion
10%
Failed body control module or internal driver circuit malfunction
Diagnostic Steps
1
Step 1: Perform visual inspection of right front and rear turn signal bulbs, checking for burned filaments, blackened glass, or physical damage. Remove bulbs and inspect sockets for corrosion, pushed-back pins, or melted plastic.
2
Step 2: Using a multimeter, test for 12V power at the turn signal bulb socket with turn signal activated. Check ground continuity from socket ground to chassis ground (should read less than 0.5 ohms).
3
Step 3: If power and ground are present at socket, install known-good bulb to verify bulb failure. If bulb is good, measure current draw in circuit (typical 1.5-2 amps per bulb) to identify excessive resistance or poor connections.
4
Step 4: Trace wiring harness from BCM to turn signal assembly, inspecting for pinched, chafed, or corroded wires. Pay special attention to areas near hinges, frame rails, and grounding points. Check connector integrity at BCM and lamp assembly.
5
Step 5: If all wiring and components test good, perform BCM output test using bidirectional controls to command right turn signal on/off while monitoring voltage and current at BCM connector pins to isolate internal BCM driver failure.
6
Step 6: After repair, clear codes, cycle turn signals multiple times, and verify proper flash rate and DTC does not return. Check that all turn signal indicators on dash function correctly.
Estimated Repair Cost
$50 - $400
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an electrical fault in the right turn signal lamp circuit. The BCM monitors current flow and has identified either an open circuit, short circuit, excessive resistance, or bulb failure in the right turn signal lighting system. This is a ...
The most common cause of B1503 (Lamp Turn Signal Right Circuit Failure) is: Burned out turn signal bulb or poor bulb socket connection with corrosion
Typical repair costs for B1503 range from $50 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is drivable but right turn signal is non-functional, creating a significant safety hazard and traffic violation. Other drivers cannot see your intention to turn or change lanes right, increasing collision risk. Repair should be completed immediately before further driving.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1503 to identify the root cause.
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Quick Info
Category
Body
System
Exterior Lighting System
Difficulty
Type
Manufacturer
Recommended Tools
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