Lamp Turn Signal Right Circuit Open
The right turn signal lamp circuit has an open connection, meaning electricity cannot flow through it properly. Think of it like a broken wire in a lamp—the light won't turn on because the circuit is incomplete.
The body control module monitors the right turn signal lamp circuit for proper current draw and continuity. When the turn signal is activated, the ECU expects to detect a specific voltage and current flowing through the lamp circuit. An open circuit prevents any current flow, causing the module to set this fault code.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Turn Signal Lamp Current Draw | 0.5-2.0 amperes when activated | No current detected or below 0.1 amperes |
| Circuit Voltage | 12V present at lamp connector | 0V or erratic voltage readings |
Code B1504 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.
Once the fault is repaired, B1504 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.