Heated Mirror Circuit Malfunction
What does B1309 mean?
The B1309 code means the vehicle's onboard diagnostic system has detected: Heated Mirror Circuit Malfunction. This is a low severity code.
Common Symptoms
- Side mirrors not defrosting
- Heated mirror indicator not working
- Fog or ice remains on mirrors
- One mirror heats but the other does not
- Rear defrost button does not activate mirror heat
Probable Causes (Ranked by Likelihood)
- Failed mirror heating element Very High
- Blown heated mirror fuse High
- Faulty rear defrost/mirror heat switch Moderate
- Corroded connector at mirror base Moderate
- Damaged wiring in door or mirror stalk Low
Step-by-Step Diagnostic Procedure
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Check heated mirror fuse
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Test for voltage at mirror connector when heat is activated
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Measure mirror heating element resistance
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Check rear defrost switch operation
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Inspect mirror connector at base of mirror for corrosion
Frequently Asked Questions
How do I know if my mirrors have heaters?
Heated mirrors are usually activated by the rear window defrost button. If your vehicle has this button and the mirrors have a wiring connector at the base, they likely have heaters.
Can I replace just the mirror glass with heater?
Yes. Heated mirror glass replacement elements are available for most vehicles and can be swapped without replacing the entire mirror assembly.
Why does one mirror heat but not the other?
Each mirror has its own heating element. If one works and the other does not, the failed mirror likely has a broken heating element or a wiring issue specific to that side.