B1684 — Mirror Driver/Passenger Switch Circuit Open

B1684 — Mirror Driver/Passenger Switch Circuit Open. A fault in the body electrical system. The car is usually drivable while you plan the repair. Typical causes: body control module (BCM) fault, corroded or loose connectors, blown fuse or failed relay.

body electrical

Is it safe to drive?

Short-term driving is OK Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm B1684 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many B0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the body electrical system for damage, corrosion, chafing or poor contact.
Subsystem check Do a continuity test end-to-end on the mirror driver/passenger switch circuit and wiggle the harness while measuring — intermittent opens show up as fluctuating readings.
Subsystem check Operate the affected function while watching its switch and motor PIDs in live data.
Subsystem check Inspect connectors and wiring at flex points (door jambs, tailgate hinges) — wires break there first.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm B1684 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1684 (parts and labor, USD, independent shop rates): BCM repair or replacement: $300–$900; Replace the switch or actuator: $120–$450; Repair wiring or connectors: $80–$250. Overall, fixing B1684 usually costs between $80 and $900. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What does OBD2 code B1684 mean?

Will B1684 clear itself?

Sometimes B1684 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

Is it safe to drive with B1684?

Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

How much does it cost to fix B1684?

BCM repair or replacement — $300–$900; Replace the switch or actuator — $120–$450; Repair wiring or connectors — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

How do I diagnose B1684 myself?

Start with a scan: confirm B1684, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the mirror driver/passenger switch, and verify the suspect component against live data before buying parts.

When a scan tool pulls code B1684, the vehicle's body control module is reporting an electrical fault in the mirror driver/passenger switch circuit. This is a body electronics code, which means it falls outside the powertrain and emissions systems. B1684 specifically indicates the circuit has gone open—the electrical pathway where the module expects to detect voltage or ground is broken. This breaks the communication between the switch and the control module, so the system cannot properly read the switch input or command mirror movement.

The body control module monitors this circuit continuously while the vehicle is running. If it fails to see the expected electrical signal for long enough across a defined number of drive cycles, it stores B1684 and triggers the warning light. The freeze frame data captured alongside this code shows the exact engine conditions—rpm, load, temperature, and speed—when the fault first appeared, giving you the best starting point for diagnosis.

Understanding how the mirror circuit works helps make sense of this code. The mirror adjustment switch sits in the driver's door and sends signals to the body control module when you press it. The module then powers the appropriate motor inside either the driver or passenger mirror to move them up, down, left, or right. When the circuit goes open, the module cannot send power to those motors and no longer receives confirmation that the switch is being pressed.

Common Symptoms of B1684

The mirror adjustment switch produces no response from either mirror
The mirror motor clicks but the glass does not move
The mirror becomes stuck in its last position and cannot be repositioned
An illuminated warning light on the dashboard
In some configurations, related body functions such as power windows or door locks may also fail
The engine and transmission operate normally—drivability is not affected

Common Causes

A loose or unplugged connector at the mirror switch or body control module
Broken wiring in the mirror switch harness, especially near door jambs where flexing occurs
A blown fuse protecting the mirror circuit
The mirror adjustment switch itself has failed internally
Corrosion on connector pins blocking electrical contact
The body control module is not processing the signal correctly
Wiring damage in areas exposed to moisture or repeated movement

How to Diagnose B1684

Connect an OBD2 scanner and confirm B1684 is stored. Record the freeze frame data—it tells you the engine conditions when the fault occurred.
Check for other body-related codes. Related codes often point to the root cause rather than B1684 itself.
Visually inspect the mirror switch, its wiring, and the connectors going to the body control module. Look for chafed insulation, broken wires, and greenish corrosion on the pins.
Perform a continuity test on the mirror switch circuit end-to-end. Wiggle the harness during the test—intermittent opens will show as fluctuating readings.
Operate the mirror switch while monitoring live data. Watch the switch state PID and motor command PID to see if the module is sending the expected signals.
Examine flex points at the door jamb and mirror mount. Wires in these areas break first because they flex every time the door opens and closes.

Repair Options and Costs

Repair costs depend entirely on which component failed. Common scenarios for B1684, including parts and labor at independent shop rates:

Repair wiring or connectors: $80–$250
Replace the mirror switch or actuator motor: $120–$450
Repair or replace the body control module: $300–$900

Always start with the least expensive and most likely causes—loose connectors and blown fuses—before replacing expensive control modules. An accurate diagnosis before buying parts saves money, and the most expensive scenario is rarely the first one to check.

Can You Drive with B1684?

Yes, in most cases B1684 does not affect engine performance, braking, or steering. The vehicle remains drivable. However, non-functional mirrors reduce visibility, which is a safety concern especially in bad weather or heavy traffic. Central locking faults associated with body control module issues can also leave the vehicle unsecured. Address B1684 before it becomes a safety problem.