What Does B1684 Mean?
This code indicates the Body Control Module (BCM) has detected an open circuit in the power mirror switch wiring or the switch itself. The BCM monitors the driver and/or passenger side mirror adjustment switch circuits and has found an interruption in electrical continuity, preventing proper mirror adjustment commands from reaching the BCM. This is a body control system fault affecting the power mirror adjustment function.
Common Causes
40%
Faulty mirror control switch with internal open circuit or broken solder joints
30%
Broken or damaged wiring harness between switch and BCM, often due to door hinge flex fatigue
20%
Corroded or loose connector terminals at switch or BCM causing intermittent open circuit
10%
Failed Body Control Module with internal circuit damage to mirror switch input
Diagnostic Steps
1
Step 1: Perform visual inspection of mirror control switch and all connectors for obvious damage, corrosion, or loose terminals. Check door harness for pinched or broken wires at door hinge area.
2
Step 2: Using a digital multimeter, test for continuity through the mirror switch in both driver and passenger positions. With switch unplugged, measure resistance across switch terminals while operating switch through all positions (expect 0-5 ohms closed, infinite ohms open).
3
Step 3: Backprobe the switch connector with multimeter and verify 12V power supply and good ground at switch connector with ignition on. If voltage absent, trace power supply circuit back toward BCM/fuse panel.
4
Step 4: Test wiring continuity from switch connector to BCM connector with switch disconnected. Measure resistance on each signal wire (should read less than 5 ohms). Wiggle door harness while testing to detect intermittent opens.
5
Step 5: If all wiring and power tests pass, substitute known-good mirror switch to confirm switch failure. If problem persists with new switch and wiring is verified good, suspect BCM internal fault.
6
Step 6: Clear codes, reconnect all components, cycle mirror switch through all positions, and verify code does not return. Test mirror operation in all directions to confirm repair.
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an open circuit in the power mirror switch wiring or the switch itself. The BCM monitors the driver and/or passenger side mirror adjustment switch circuits and has found an interruption in electrical continuity, preventing proper mirror ...
The most common cause of B1684 (Mirror Driver/Passenger Switch Circuit Open) is: Faulty mirror control switch with internal open circuit or broken solder joints
Typical repair costs for B1684 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This is safe to drive with as it only affects mirror adjustment convenience features. Mirrors can typically be adjusted manually if needed, though this is inconvenient. Repair can be scheduled at convenience.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1684 to identify the root cause.
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Quick Info
Category
Body
System
Body Control and Convenience Systems
Difficulty
Type
Manufacturer
Recommended Tools
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