B1785 — Mirror Passenger Up Circuit Short To Ground #

Note: The exact wording of this code may differ depending on the vehicle manufacturer.

• B1785 – Door Mirror Passenger Up Circuit Short To Ground (Toyota/Lexus)
• B1785 – Outside Mirror Up Signal Short to Ground (Nissan/Infiniti)
• B1785 – Passenger Mirror Motor Up Control Circuit Short to Ground (Honda/Acura)

Summary of DTC B1785 #

DTC B1785 indicates that the passenger side mirror up control circuit is experiencing a short to ground. In simpler terms, the electrical pathway responsible for moving the mirror upward is unintentionally connected to the vehicle’s ground, causing improper or non-functional movement. This code is most often set by the vehicle’s Body Control Module (BCM) or the Mirror Control Module after detecting abnormal voltage levels in the circuit. While this issue rarely disables the vehicle, it can affect mirror adjustability and, by extension, driving safety and comfort.

Common Symptoms for Code B1785 #

When B1785 is present, you may notice a range of issues related to the passenger side mirror’s ability to move. The most frequent symptoms include:

• Passenger side mirror cannot move upward when operated from the switch.
• Mirror moves only in some directions (left, right, down) but not up.
• Unusual clicking or buzzing sounds from the mirror area when attempting to adjust up.
• Mirror adjustment switch feels unresponsive or only partially functional.
• In rare cases, blown fuse for the mirror circuit.

Probable Causes for Code B1785 #

Several underlying issues can trigger a B1785 code. The most frequent causes, in order of likelihood, include:

1. Shorted wiring: Damaged or pinched wire in the mirror up control circuit contacting ground.
2. Faulty mirror motor: The internal motor for the passenger mirror up function has shorted internally.
3. Defective mirror adjustment switch: The switch itself may be allowing current to flow directly to ground.
4. Connector corrosion or water intrusion: Moisture in connectors can create a path to ground.
5. Faulty Body Control Module (BCM) or Mirror Control Module: Rare, but possible if other causes are eliminated.

Step-by-Step Diagnostic Procedure for B1785 #

Proper diagnosis ensures you repair the actual cause and avoid unnecessary parts replacement. Here’s a proven step-by-step approach:

1. Confirm the code using a professional OBD-II scan tool and check for related codes.
2. Check mirror operation from the switch—does up movement fail while other directions work?
3. Inspect wiring between the mirror, switch, and control module for visible damage, pinching, or exposed copper.
4. Disconnect the mirror and switch connectors; check for corrosion, moisture, or bent pins.
5. Test for continuity to ground on the mirror up wire with a multimeter—there should be none with the switch off.
6. Test the mirror motor by applying 12V and ground directly to the up terminals (bench test if possible).
7. Test the adjustment switch for internal shorts using an ohmmeter.
8. Check fuses and replace if blown; if a fuse blows again, suspect a dead short.
9. As a last resort, swap in a known-good mirror assembly or switch to isolate the fault.

Possible Repairs for Code B1785 #

Repairs depend on the root cause found during diagnostics. Typical solutions include:

• Repair or replace damaged wiring that is shorted to ground.
• Replace the passenger mirror motor if internal short is confirmed.
• Replace the mirror adjustment switch if it’s internally shorted.
• Clean or replace corroded connectors and apply dielectric grease if needed.
• Replace the Body Control Module (BCM) or Mirror Control Module only if all other components test good and fault persists (rare).

Is It Safe to Drive with Code B1785? #

Yes, you can usually continue to drive your vehicle with code B1785 present. This code does not affect essential driving functions or engine performance. However, the inability to adjust the passenger side mirror upward can reduce visibility and convenience, especially when multiple drivers use the vehicle. Plan to address the root cause soon to restore full mirror functionality and maximize safety.

Vehicles Most Commonly Affected by B1785 #

While B1785 can occur on many modern vehicles with power mirrors, it’s most frequently reported on:

• Toyota Camry, Corolla, RAV4, Highlander
• Lexus RX, ES, IS series
• Nissan Altima, Maxima, Rogue
• Honda Accord, Civic, CR-V
• Acura TL, MDX
• Some Hyundai and Kia models with power mirrors

This code may also appear on other vehicles with similar electrical architectures, especially from Asian OEMs.

Common Mistakes & Best Practices for B1785 #

Avoiding misdiagnosis is key to a quick and cost-effective repair. Here are some pitfalls and recommended practices:

• Replacing the mirror motor or switch without testing the wiring first—wiring is the most common cause.
• Ignoring connector corrosion—it can intermittently short to ground.
• Overlooking fuse replacement—a blown fuse can mask the original short.
• Not verifying repair by clearing the code and retesting—the code may return if the root cause isn’t addressed.
• Always use OEM parts for mirror assemblies to ensure compatibility and reliability.

Express FAQ About Code B1785 #

Here are quick answers to the most common questions about B1785:

• Q: Will disconnecting the battery clear code B1785?
  A: Disconnecting the battery may clear the code temporarily, but it will return unless the underlying fault is repaired.
• Q: Can I fix B1785 myself?
  A: If you’re comfortable with basic electrical testing and have access to a multimeter, you can check for obvious wiring issues. For anything beyond that, professional diagnosis is recommended.