What Does B1740 Mean?
This code indicates the Body Control Module (BCM) has detected a short to ground in the driver's side power mirror horizontal (left/right) adjustment switch circuit. When the switch is activated, the BCM detected voltage lower than expected, indicating the circuit is grounded when it should not be. This prevents proper horizontal adjustment of the driver's side mirror.
Common Causes
40%
Damaged or chafed wiring in the driver's door harness causing short to ground
30%
Failed mirror switch assembly with internal short to ground
20%
Corroded or damaged mirror switch connector pins creating ground path
10%
Faulty Body Control Module with internal short detection circuit malfunction
Diagnostic Steps
1
Step 1: Perform visual inspection of the driver's door wiring harness, especially where it flexes between door and body. Look for pinched, chafed, or damaged wires that may be contacting ground
2
Step 2: Disconnect the mirror switch connector and use a digital multimeter to measure resistance between the horizontal switch signal wire (typically identified in wiring diagram) and ground with switch in neutral position. Reading should be infinite; continuity indicates short to ground
3
Step 3: If no short found at switch connector, disconnect BCM connector and measure resistance from the horizontal switch signal circuit pin to ground. This isolates whether short is in switch, harness, or BCM
4
Step 4: If short is isolated to switch, replace mirror switch assembly. If short is in harness, repair or replace damaged section of door harness, paying special attention to door hinge area
5
Step 5: After repair, reconnect all components, clear codes, and verify mirror horizontal adjustment functions properly in both directions. Confirm DTC does not return
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected a short to ground in the driver's side power mirror horizontal (left/right) adjustment switch circuit. When the switch is activated, the BCM detected voltage lower than expected, indicating the circuit is grounded when it should not be. ...
The most common cause of B1740 (Mirror Driver Horizontal Switch Circuit Short To Ground) is: Damaged or chafed wiring in the driver's door harness causing short to ground
Typical repair costs for B1740 range from $100 to $450, 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 features. Repair at convenience, though proper mirror adjustment is important for safe lane changes and visibility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1740 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 Control and Accessories
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
