B1779 — Mirror Driver Down Circuit Open #

Note: The description of code B1779 can vary depending on the vehicle manufacturer (OEM). Always refer to your specific service manual for the most accurate terminology.

• Mirror Driver Down Circuit Open (Generic, Ford, Toyota, Nissan, Honda, Hyundai, Kia, GM)
• Mirror Driver Down Switch Circuit Open (Lexus, Toyota)
• Left Mirror Down Motor Circuit Open (Chrysler, Dodge, Jeep)
• Driver-Side Mirror Down Control Open Circuit (Mazda, Subaru)

Code summary for B1779 #

The B1779 diagnostic trouble code (DTC) refers to an open circuit condition detected in the driver’s side power mirror “down” control wiring. This means the vehicle’s body control module (BCM) or door control module is unable to detect proper continuity when commanding the driver’s mirror to tilt downward. Such a code is typically triggered by a wiring break, a disconnected harness, or a malfunction in the mirror adjustment switch or motor. This code does not affect engine performance, but can impact convenience and mirror safety features. Prompt attention is recommended, especially if you rely on power mirror adjustments for visibility.

Common symptoms for code B1779 #

When the B1779 code appears, it’s usually accompanied by clear signs that your driver’s side mirror isn’t behaving as expected. Have you noticed your mirror refusing to tilt down, no matter how many times you tap the adjustment switch? Maybe you hear silence instead of the familiar hum of the mirror motor. These are classic symptoms, and they can be frustrating, especially when you need to adjust for parking or lane changes.

• Driver’s side mirror does not move downward when commanded
• No sound or response from the mirror adjustment motor (down direction only)
• Mirror may still move left, right, or up (other directions unaffected)
• Possible warning light or error message on dashboard (in vehicles with power mirror monitoring)
• Intermittent function, especially if wiring is loose or corroded

Most likely causes for B1779 #

Some causes are more common than others when it comes to an open circuit in the mirror’s down control. The culprit is often as simple as a broken wire—think of it like a string of Christmas lights, where one bad bulb ruins the whole show. But it could also be a faulty switch, a bad ground, or an issue with the mirror’s own motor. Here’s what technicians see most frequently, in order of likelihood:

1. Broken or damaged wiring in the driver’s mirror down circuit (often at the door hinge or connector)
2. Loose or corroded electrical connectors at the mirror, switch, or control module
3. Faulty driver’s side mirror adjustment switch
4. Failed mirror motor (down direction only)
5. Defective body control module (BCM) or door module (less common)

Step-by-step diagnosis for code B1779 #

Diagnosing B1779 is a logical process, and with a basic multimeter and some patience, you can track down the problem. Think of yourself as a detective, following the trail from the switch to the mirror, checking every possible link in the chain. Here’s a proven method:

• Scan for additional DTCs: Record any other codes related to mirrors, doors, or BCM. This helps spot related issues.
• Test mirror switch function: Operate the mirror in all directions. Does only the down function fail?
• Inspect wiring at the door hinge: Gently flex the wiring harness while commanding the mirror down. Look for intermittent operation.
• Check mirror and switch connectors: Unplug, inspect for corrosion, bent pins, or loose fit. Clean and reconnect.
• Measure voltage at the mirror motor: With the down command pressed, use a multimeter to ensure voltage is reaching the motor. No voltage? Trace back to the switch/module.
• Test continuity of the down circuit wire: Use the multimeter’s continuity function to confirm the wire isn’t broken between switch/module and mirror.
• Swap with known good parts if needed: If wiring and connectors check out, substitute the switch or mirror with a known good one, if available.

Possible repairs for code B1779 #

Once you’ve found the weak link, fixing B1779 can be straightforward or may require some hands-on work—think of it as patching a leaky hose or replacing a burnt-out bulb. Here are the most effective repairs, matched to the likely causes:

• Repair or replace damaged wiring in the door harness, especially at flex points
• Clean, tighten, or replace connectors at the mirror, switch, or control module
• Replace the mirror adjustment switch if confirmed faulty
• Replace the driver’s side mirror assembly if the down motor is dead
• Repair or replace BCM/door control module (rare—do this only after confirming all other components are good)

Is it safe to drive with code B1779? #

Yes, you can continue driving with code B1779. This fault only affects the power adjustment of your driver’s side mirror in the down direction; it does not impact critical safety or engine systems. However, be aware that improper mirror positioning can limit visibility, especially during parking or reversing. If you rely on frequent mirror adjustments, repair the issue soon to maintain optimal safety.

Vehicles most commonly affected by B1779 #

While any vehicle with power mirrors can set a B1779 code, some makes and models show this issue more often—usually due to wiring flex or component design. Here are vehicles where technicians report this code most frequently:

• Ford F-Series (F-150, F-250, etc.)
• Toyota Camry, Corolla, RAV4
• Nissan Altima, Maxima
• Honda Accord, Civic, CR-V
• Hyundai Sonata, Elantra
• Kia Optima, Sorento
• GM Silverado, Sierra, Malibu

Common mistakes and best practices for B1779 #

Even seasoned DIYers and technicians can misdiagnose B1779, especially when jumping to conclusions without checking the basics. Avoid the temptation to swap parts blindly—use methodical testing to save time, money, and frustration.

• Don’t replace the mirror motor or switch before checking wiring and connectors
• Always inspect the door harness at the hinge—this is a high-stress area prone to breaks
• Use dielectric grease on connectors to prevent future corrosion
• Clear the code and retest after repairs to confirm success
• Double-check wiring diagrams for your exact vehicle model and year

Quick FAQ for B1779 #

Still have questions? Here are the answers to some of the most common concerns:

• Q: Will B1779 affect my power folding mirror function?
  A: No, this code is specific to the “down” movement. Folding functions use separate circuits and motors.
• Q: Can I reset the code by disconnecting the battery?
  A: You may clear the code temporarily, but it will return as soon as the circuit fault is detected again. The root cause must be repaired to resolve B1779 permanently.
• Q: If I replace the mirror, do I need to reprogram anything?
  A: In most cases, no. However, some vehicles with memory mirrors or advanced modules may require calibration. Always follow OEM procedures.