What Does B1646 Mean?
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected a short circuit to ground in the electrical circuit controlling the passenger side (right) power mirror. The BCM monitors current flow and voltage in the mirror control circuits, and when voltage drops to near zero volts or excessive current is detected on the control wires, it sets this code. This fault prevents proper operation of the passenger mirror adjustment functions.
Common Causes
45%
Damaged or chafed wiring harness in mirror assembly or door jamb area causing wire insulation to contact ground
30%
Failed passenger mirror motor assembly with internal short to ground
15%
Water intrusion or corrosion in mirror connector causing short circuit path to ground
10%
Faulty Body Control Module mirror control output driver circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of passenger mirror assembly, door jamb area, and all visible wiring for obvious damage, chafing, pinching, or corrosion. Check mirror connector for water intrusion, corroded pins, or pushed-back terminals.
2
Step 2: Disconnect the passenger mirror electrical connector and use a digital multimeter to measure resistance between each mirror control wire and ground. Readings should be greater than 10k ohms; any reading below 100 ohms indicates a short to ground in the wiring or mirror assembly.
3
Step 3: With mirror disconnected, clear codes and attempt to recreate the fault. If code does not return, the mirror motor assembly is faulty. If code immediately returns, the short is in the vehicle wiring harness between BCM and mirror connector.
4
Step 4: If wiring harness is suspect, carefully inspect wire routing through door jamb boot and A-pillar area where flexing occurs. Use continuity test to isolate exact location of short. Repair or replace affected wiring section.
5
Step 5: After repair, reconnect all components, clear codes, and test mirror operation in all directions (up, down, left, right). Verify no codes return and BCM shows normal mirror control circuit operation.
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected a short circuit to ground in the electrical circuit controlling the passenger side (right) power mirror. The BCM monitors current flow and voltage in the mirror control circuits, and when voltage drops to near zer...
The most common cause of B1646 (Mirror Passenger Right Circuit Short To Ground) is: Damaged or chafed wiring harness in mirror assembly or door jamb area causing wire insulation to contact ground
Typical repair costs for B1646 range from $100 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This fault does not affect vehicle safety or driveability and the vehicle is safe to continue driving. The passenger mirror adjustment function will be inoperative, which may affect blind spot visibility when mirror repositioning is needed. Repair at your convenience within a reasonable timeframe.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1646 to identify the root cause.
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Quick Info
Category
Body
System
Body Control and Accessories
Difficulty
Type
Manufacturer
Recommended Tools
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