What Does B1784 Mean?
This code indicates that the Body Control Module (BCM) has detected an abnormal voltage condition in the passenger side mirror upward movement circuit. Specifically, the circuit is showing battery voltage when it should be at a lower voltage or ground, suggesting a short to power condition. This prevents proper control of the passenger mirror's upward adjustment function.
Common Causes
45%
Damaged or chafed wiring harness between BCM and passenger mirror causing short to battery voltage
30%
Faulty passenger side mirror motor assembly with internal short to power
15%
Shorted mirror control switch internally providing constant power to circuit
10%
Corroded or damaged door harness connector pins causing cross-circuit short
Diagnostic Steps
1
Step 1: Perform visual inspection of passenger mirror wiring harness from door jamb through door to mirror assembly, looking for pinched, chafed, or damaged wires especially at hinge points and flex areas
2
Step 2: Disconnect the passenger side mirror electrical connector and measure voltage on the mirror UP circuit wire at the vehicle harness side with ignition on - should read 0V; if battery voltage is present, wiring harness has short to power between BCM and connector
3
Step 3: If no voltage found at disconnected mirror connector, measure resistance between mirror UP circuit terminal and battery positive at the mirror side of connector - high resistance indicates mirror motor internal short; low resistance confirms mirror motor fault
4
Step 4: If mirror motor tests good, disconnect mirror control switch and check for voltage on UP circuit - if voltage disappears, switch is faulty and providing constant power
5
Step 5: Inspect door harness connector for corrosion, bent pins, or moisture intrusion that could cause cross-circuit shorts; clean and repair as needed
6
Step 6: Clear codes, reconnect all components, cycle mirror controls through all positions and verify proper operation, then road test and confirm code does not return
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) has detected an abnormal voltage condition in the passenger side mirror upward movement circuit. Specifically, the circuit is showing battery voltage when it should be at a lower voltage or ground, suggesting a short to power condition. This pre...
The most common cause of B1784 (Mirror Passenger Up Circuit Short To Battery) is: Damaged or chafed wiring harness between BCM and passenger mirror causing short to battery voltage
Typical repair costs for B1784 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 passenger mirror adjustment functionality. The mirror itself remains usable in its current position, though manual adjustment capability may be limited. Repair at convenience but address to maintain full visibility adjustment.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1784 to identify the root cause.
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Quick Info
Category
Body
System
Power Mirror System
Difficulty
Type
Manufacturer
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