What Does B1779 Mean?
This code indicates that the Body Control Module (BCM) has detected an open circuit in the driver's side mirror downward adjustment motor or its associated wiring. When the mirror down command is issued, the BCM cannot complete the circuit, suggesting a break in the electrical path between the control module and the mirror motor. This prevents the driver's mirror from tilting downward when the adjustment switch is activated.
Common Causes
40%
Broken or damaged wiring between the BCM and driver's mirror assembly, often in the door hinge area where flexing occurs
30%
Failed mirror motor assembly with internal open circuit in the downward tilt motor winding
20%
Corroded or loose electrical connector at the mirror or BCM connection point
10%
Faulty BCM with failed output driver circuit for mirror down control
Diagnostic Steps
1
Step 1: Perform visual inspection of the driver's door wiring harness, especially in the door hinge area where wires flex. Look for damaged, pinched, or broken wires and inspect all connectors for corrosion, bent pins, or looseness
2
Step 2: With ignition on, use a digital multimeter to check for battery voltage at the mirror connector when commanding mirror down. Backprobe the connector while activating the mirror switch to verify power and ground signals reach the mirror
3
Step 3: Disconnect the mirror connector and measure resistance across the mirror motor down circuit terminals (typically 2-8 ohms for a functional motor). An infinite resistance reading confirms an open circuit in the motor itself
4
Step 4: If wiring and mirror test good, check BCM output by measuring voltage at the BCM connector terminal for mirror down circuit while commanding operation. Lack of voltage indicates BCM failure
5
Step 5: Repair or replace identified faulty component (wiring, connector, mirror assembly, or BCM), then clear codes and verify mirror operation in all directions to confirm repair
Estimated Repair Cost
$100 - $600
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) has detected an open circuit in the driver's side mirror downward adjustment motor or its associated wiring. When the mirror down command is issued, the BCM cannot complete the circuit, suggesting a break in the electrical path between the contr...
The most common cause of B1779 (Mirror Driver Down Circuit Open) is: Broken or damaged wiring between the BCM and driver's mirror assembly, often in the door hinge area where flexing occurs
Typical repair costs for B1779 range from $100 to $600, 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 functionality and does not impact vehicle operation or safety systems. Repair at your convenience, though proper mirror adjustment is important for optimal visibility and safe lane changes.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1779 to identify the root cause.
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Quick Info
Category
Body
System
Body Control System - Power Mirror Assembly
Difficulty
Type
Manufacturer
Recommended Tools
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