What Does B1783 Mean?
This code indicates the Body Control Module (BCM) has detected an open circuit in the passenger side mirror upward movement control circuit. When the mirror adjustment switch is commanded to move the passenger mirror upward, the BCM is unable to complete the electrical circuit, suggesting a break in the wiring, a faulty connection, or a defective mirror motor. This is a manufacturer-specific code that affects the power mirror adjustment system.
Common Causes
40%
Broken or damaged wiring between BCM and passenger mirror assembly, often at the door hinge flex point where wires bend repeatedly
30%
Faulty passenger mirror motor or internal mirror motor circuit board failure
20%
Corroded or loose electrical connector at passenger mirror or door module
10%
Failed mirror control switch or BCM internal circuit fault
Diagnostic Steps
1
Step 1: Perform visual inspection of passenger door wiring harness, particularly at door hinge area and mirror base, checking for broken, pinched, or damaged wires and corroded connectors
2
Step 2: Using a digital multimeter, check for continuity in the mirror up circuit from the BCM connector to the mirror motor connector with ignition off, expecting less than 5 ohms resistance
3
Step 3: With ignition on and mirror switch activated to 'up' position, backprobe the mirror motor connector and verify presence of battery voltage (typically 12V) and ground signal from BCM
4
Step 4: If voltage and ground are present at connector, remove mirror assembly and bench test the mirror motor by applying direct 12V power and ground to the up circuit terminals to verify motor operation
5
Step 5: If motor operates on bench test, inspect mirror connector terminals for corrosion, spread pins, or pushed-back pins; if motor fails bench test, replace mirror assembly
6
Step 6: After repair, clear codes, cycle mirror through all positions multiple times, and verify no code returns and proper operation is restored
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an open circuit in the passenger side mirror upward movement control circuit. When the mirror adjustment switch is commanded to move the passenger mirror upward, the BCM is unable to complete the electrical circuit, suggesting a break in...
The most common cause of B1783 (Mirror Passenger Up Circuit Open) is: Broken or damaged wiring between BCM and passenger mirror assembly, often at the door hinge flex point where wires bend repeatedly
Typical repair costs for B1783 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 and does not impact vehicle safety systems. Repair at your convenience, though proper mirror positioning is important for 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 B1783 to identify the root cause.
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Quick Info
Category
Body
System
Power Mirror System
Difficulty
Type
Manufacturer
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