What Does B1748 Mean?
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected a short to ground in the electrical circuit controlling the horizontal adjustment switch for the passenger side mirror. The BCM monitors voltage and resistance in the switch circuit and has identified an abnormal low resistance path to ground, preventing proper mirror adjustment control. This is a manufacturer-specific body control code that affects the power mirror adjustment system.
Common Causes
40%
Damaged or chafed wiring in the door harness between the switch and mirror motor, typically where the harness flexes at the door hinge
30%
Failed passenger mirror horizontal adjustment switch with internal short to ground
20%
Corroded or moisture-damaged mirror motor connector causing short circuit
10%
Failed Body Control Module with internal circuit fault on mirror control output
Diagnostic Steps
1
Step 1: Perform visual inspection of passenger door wiring harness, particularly at the door hinge area and mirror base, looking for pinched, chafed, or damaged wires that may be contacting ground
2
Step 2: Disconnect the passenger mirror motor connector and use a digital multimeter to measure resistance between the horizontal switch control circuit terminal and ground with switch in neutral position (should read infinite/open circuit); if resistance is below 10k ohms, problem is in wiring or switch
3
Step 3: Disconnect the mirror control switch assembly and measure resistance between the horizontal switch signal wire and ground at the BCM connector side (should read open circuit); if short remains, repair wiring harness; if short clears, replace mirror switch assembly
4
Step 4: If wiring tests normal, reconnect all components except suspect switch or motor, clear codes, and operate mirror control while monitoring live data to isolate whether switch or motor is causing the short to ground condition
5
Step 5: After repair, verify proper mirror operation in all directions, clear diagnostic codes, and perform a road test with multiple door open/close cycles to confirm repair and ensure code does not return
Estimated Repair Cost
$120 - $450
Parts + labor, varies by vehicle and location
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected a short to ground in the electrical circuit controlling the horizontal adjustment switch for the passenger side mirror. The BCM monitors voltage and resistance in the switch circuit and has identified an abnormal ...
The most common cause of B1748 (Mirror Passenger Horizontal Switch Circuit Short To Ground) is: Damaged or chafed wiring in the door harness between the switch and mirror motor, typically where the harness flexes at the door hinge
Typical repair costs for B1748 range from $120 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This code does not affect vehicle safety or driveability and the vehicle is safe to operate. The only concern is reduced visibility due to inability to properly adjust the passenger mirror, which should be corrected at the driver's earliest convenience.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1748 to identify the root cause.
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Quick Info
Category
Body
System
Body Control / Power Mirror System
Difficulty
Type
Manufacturer
Recommended Tools
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