B1746 — Mirror Passenger Horizontal Switch Circuit Open

OBD2 code B1746 flags a problem with the body electrical system (mirror passenger horizontal switch circuit open). The car is usually drivable while you plan the repair. Common culprits: corroded or loose connectors, body control module (BCM) fault, damaged wiring in door jambs or wet areas.

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 B1746 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 passenger horizontal 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 B1746 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1746 (parts and labor, USD, independent shop rates): BCM repair or replacement: $300–$900; Repair wiring or connectors: $80–$250; Replace the switch or actuator: $120–$450. Overall, fixing B1746 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

How much does it cost to fix B1746?

BCM repair or replacement — $300–$900; Repair wiring or connectors — $80–$250; Replace the switch or actuator — $120–$450. 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 B1746 myself?

Start with a scan: confirm B1746, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the mirror passenger horizontal switch, and verify the suspect component against live data before buying parts.

What does OBD2 code B1746 mean?

Will B1746 clear itself?

Sometimes B1746 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 B1746?

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.

When your scan tool pulls code B1746, the underlying issue lies entirely within the body's electrical network rather than the engine or drivetrain. Specifically, the body control module has detected that the passenger-side mirror horizontal adjustment switch circuit is not completing its expected electrical path. In plain terms, the circuit is open — meaning no current can flow through the switch and associated wiring the way the module expects when you try to move the mirror horizontally.

The passenger mirror adjustment system operates through a straightforward circuit: the switch sends a signal to the body control module, which then energizes a small electric motor inside the mirror housing to move the glass left or right. When this switch circuit develops an open condition — whether from a broken wire, a corroded connector, a blown fuse, or an internally failed switch — the electrical loop cannot be completed. The module monitors this circuit continuously while the vehicle is running and compares the actual readings against factory-calibrated parameters. When those readings fall outside acceptable limits for the required number of consecutive drive cycles, the module stores B1746 and often illuminates a warning light on the instrument cluster.

The freeze frame data stored alongside B1746 is your diagnostic starting point. This snapshot captures engine speed, load percentage, coolant temperature, vehicle speed, and other sensor readings the moment the fault was detected. Since an intermittent electrical problem may only appear under specific conditions — such as when the door is fully closed and the wiring flexes — having this recorded data helps you replicate the exact circumstances during your troubleshooting.

Symptoms of B1746

The check engine or body control warning light stays illuminated
Engine performance and fuel economy remain unaffected in most vehicles
The passenger mirror fails to move horizontally when the switch is operated
The mirror may work intermittently, responding only to certain switch positions or temperatures
Related mirror functions (vertical adjustment or heated mirrors) continue operating normally in some cases
The affected function works unpredictably — working one day and failing the next, particularly in cold or wet weather

Common Causes

The most frequent culprit behind B1746 is a failed passenger mirror horizontal adjustment switch itself — these switches experience heavy use and their internal contacts wear out over time. Wiring harness damage ranks second, particularly in the door boot where wires flex every time the door opens and closes. Corroded or loose connectors at the mirror, door junction, or body control module can also create an open circuit. Less commonly, a blown fuse dedicated to the mirror circuit will prevent operation entirely. The body control module itself can fail, though this represents a less common scenario. Wiring damaged by moisture intrusion in door jambs or tailgate hinges creates intermittent opens that are difficult to track down. In some cases, a failed mirror motor or actuator shares the same ground or signal circuit, causing the module to misinterpret the condition.

Diagnosing B1746

Connect your OBD2 scanner, retrieve code B1746, and record all freeze frame data before clearing anything — this information shows the exact conditions when the fault occurred and guides your inspection strategy.
Check for any additional stored codes. Related body electrical codes often point to the root cause, such as a shared ground or power supply issue. Search for technical service bulletins specific to your make, model, and model year using your VIN at the manufacturer website or nhtsa.gov — many B1746-related issues have documented factory remedies or software recalibrations.
Perform a thorough visual inspection of the wiring harness between the door hinge and the mirror assembly. Look for chafed insulation, broken strands visible through the wire jacket, and any signs of moisture damage or corrosion on the connector pins.
Test circuit continuity from the switch connector to the body control module input. Use a multimeter set to resistance mode and wiggle the harness during testing — an intermittent open will show as fluctuating resistance readings that spike when the wire flexes.
Operate the mirror switch while monitoring voltage or resistance at the mirror motor connector in live data mode if your scan tool supports it. No voltage change when the switch is pressed confirms the open is upstream of the motor.
Examine connectors at both the mirror housing and the door jamb pass-through. Back-out pins, pushed-out terminals, and greenish corrosion deposits all indicate poor connections capable of generating B1746.
Clear the code, complete a drive cycle that replicates the freeze frame conditions, and verify B1746 does not return before considering the repair complete.

Repair Options and Costs

Depending on which component is actually at fault, repair costs vary considerably. A faulty mirror adjustment switch typically requires mirror assembly replacement or switch repair, running $120–$450 for parts and labor. Wiring harness repairs — whether a damaged section needs splicing, terminals require cleaning, or connectors need replacement — generally cost $80–$250. Body control module diagnosis, repair, or replacement is the most expensive scenario, ranging from $300–$900 depending on whether the module can be reprogrammed or requires physical replacement.

Driving Safety Verdict

B1746 carries a short severity rating. The mirror adjustment fault has no impact on engine operation, braking, steering, or occupant safety systems. You can continue driving normally while scheduling the repair. The only practical concern arises if the mirror failure occurs in poor visibility conditions where rearward visibility is already compromised, or if the same underlying electrical issue eventually affects unrelated body functions — but this represents an unlikely worst-case scenario rather than a direct consequence of B1746.