Heated Mirror Circuit Malfunction
What does B1109 mean?
The B1109 code means the vehicle's onboard diagnostic system has detected: Heated Mirror Circuit Malfunction. This is a low severity code.
Common Symptoms
- Side mirrors do not defrost
- Mirror glass stays foggy or iced over
- Mirror heater indicator light not working
- One mirror heats but the other does not
- Rear defroster works but mirror heaters do not
Probable Causes (Ranked by Likelihood)
- Burned out mirror heating element Very High
- Faulty mirror heater relay or switch High
- Broken wire in mirror harness Moderate
- BCM heated mirror output failure Low
Step-by-Step Diagnostic Procedure
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Activate mirror heater and check for warmth on glass
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Test voltage at mirror heater connector
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Check mirror heater resistance with multimeter
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Inspect mirror wiring for continuity
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Verify heater relay or switch operation
Frequently Asked Questions
How do mirror heaters work?
Mirror heaters use a thin resistive heating element bonded to the back of the mirror glass. When activated, it warms the glass to prevent fogging and melt ice.
Are mirror heaters linked to the rear defroster?
On many vehicles, the heated mirrors activate automatically when the rear window defroster is turned on. Some vehicles have a separate mirror heater button.
Can I replace just the heating element?
On some vehicles, the heated mirror glass can be replaced separately from the mirror housing. On others, the entire mirror assembly must be replaced.