Left Turn Signal Circuit Malfunction
What does B1003 mean?
The B1003 code means the vehicle's onboard diagnostic system has detected: Left Turn Signal Circuit Malfunction. This is a moderate severity code.
Common Symptoms
- Left turn signal not flashing
- Rapid turn signal clicking (hyperflash)
- Left turn signal indicator on dash stays solid
- Turn signal works intermittently
- Hazard lights left side not working
Probable Causes (Ranked by Likelihood)
- Burned out left turn signal bulb Very High
- Corroded bulb socket or ground connection High
- Faulty turn signal relay or flasher module Moderate
- Damaged wiring to left turn signal Moderate
- Multifunction switch (turn signal stalk) failure Low
Step-by-Step Diagnostic Procedure
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Check all left turn signal bulbs front and rear
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Inspect bulb sockets for corrosion
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Test ground connections at each light housing
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Check turn signal relay or flasher unit
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Test multifunction switch operation with scan tool
Frequently Asked Questions
Why is my turn signal clicking really fast?
Rapid clicking (hyperflash) almost always means a turn signal bulb has burned out. The flasher detects the lower current draw from the missing bulb and flashes faster to alert you.
Can I replace the turn signal bulb myself?
Yes. Turn signal bulbs are usually easy to access from behind the headlight or tail light assembly. Some vehicles require removing a few screws to access the bulb socket.
Is driving without a turn signal legal?
No. Working turn signals are required by law in all states. You can be cited for a non-functioning turn signal, and it creates a safety hazard for other drivers.