What Does B1785 Mean?
This code indicates the Body Control Module (BCM) has detected a short to ground in the electrical circuit controlling the upward movement of the passenger side mirror. The BCM monitors voltage and current in the mirror motor circuit and sets this code when it detects abnormally low resistance, indicating the circuit is grounded when it should not be. This affects the power mirror adjustment system, specifically preventing proper upward adjustment of the passenger mirror.
Common Causes
45%
Damaged or chafed wiring in the door harness between door jamb and mirror, causing conductor to contact ground
30%
Failed mirror motor assembly with internal short to ground in upward movement circuit
15%
Water intrusion or corrosion in mirror connector causing short circuit path to ground
10%
Faulty mirror switch assembly with internal short sending ground signal on up circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of passenger door wiring harness, especially at door hinge area and mirror base. Look for pinched, chafed, or damaged wires. Check mirror connector for water intrusion, corrosion, or damaged pins.
2
Step 2: Disconnect passenger mirror connector. Using a digital multimeter, measure resistance between the mirror up control circuit wire (at vehicle harness side) and ground. Should read infinite resistance (open circuit). If less than 10,000 ohms, wiring harness has short to ground between BCM and connector.
3
Step 3: If harness tests good, reconnect mirror and disconnect mirror switch. Test resistance from mirror up circuit to ground again. If now shows infinite resistance, switch assembly is faulty. If still shows low resistance, proceed to Step 4.
4
Step 4: With mirror connector disconnected, measure resistance between mirror up motor terminal and mirror housing ground. Should read between 3-10 ohms for motor coil, but completely isolated from housing ground. If continuity exists to housing, mirror motor has internal short.
5
Step 5: Repair identified fault (replace harness section, mirror assembly, or switch). Clear codes, perform mirror function test in all directions, and verify code does not return after multiple operation cycles.
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected a short to ground in the electrical circuit controlling the upward movement of the passenger side mirror. The BCM monitors voltage and current in the mirror motor circuit and sets this code when it detects abnormally low resistance, indi...
The most common cause of B1785 (Mirror Passenger Up Circuit Short To Ground) is: Damaged or chafed wiring in the door harness between door jamb and mirror, causing conductor to contact ground
Typical repair costs for B1785 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this only affects mirror adjustment convenience feature. Repair at earliest convenience to restore full mirror functionality for proper blind spot visibility adjustment.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1785 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Body
System
Body Electronics - Power Mirror System
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
