B1737 — Mirror Driver Horizontal Switch Circuit Failure

OBD2 code B1737 flags a problem with the body electrical system (mirror driver horizontal switch circuit failure). The car is usually drivable while you plan the repair. Common culprits: blown fuse or failed relay, body control module (BCM) fault, corroded or loose connectors.

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 B1737 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 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 B1737 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1737 (parts and labor, USD, independent shop rates): Replace the switch or actuator: $120–$450; Repair wiring or connectors: $80–$250; BCM repair or replacement: $300–$900. Overall, fixing B1737 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 do I diagnose B1737 myself?

Start with a scan: confirm B1737, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the mirror driver horizontal switch circuit, and verify the suspect component against live data before buying parts.

Will B1737 clear itself?

Sometimes B1737 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.

How much does it cost to fix B1737?

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

What are the symptoms of B1737?

Drivers most often notice: warning light on the dashboard, the affected function (locks, windows, lighting, wipers) works intermittently or not at all, no impact on engine operation in most cases.

Is it safe to drive with B1737?

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.

B1737 is a body electrical fault code that points to a problem with the driver's side mirror's horizontal adjustment switch circuit. When the vehicle's control module detects that the mirror's horizontal positioning circuit has failed—either because it's sending an open signal, a short, or readings outside expected parameters—it logs B1737 and often illuminates a warning light on the instrument cluster. This code lives in the B-body category, which covers comfort and convenience systems rather than engine management.

The affected system involves a simple but essential circuit: when you press the left or right arrow on the mirror control switch, you complete a path that tells the mirror motor which direction to move. The control module constantly monitors that circuit. If it sees voltage where it shouldn't, no voltage where it should, or resistance values that don't match the calibration, the module flags the fault. Most manufacturers require the condition to appear across multiple drive cycles before storing a permanent code, which helps rule out temporary electrical glitches. When you pull the code with a scanner, it typically comes with a freeze-frame snapshot—engine load, coolant temperature, vehicle speed, and RPM at the exact moment the fault was detected. That data narrows down whether the problem is intermittent or tied to specific conditions like cold starts or high electrical load.

Common Symptoms of B1737

The driver's mirror fails to adjust left or right from the control switch
The mirror may be stuck in one position or move in only one direction
The mirror adjustment switch feels unresponsive or the indicator light dims
The malfunction indicator lamp (MIL) stays illuminated on the dashboard
The problem can be intermittent—working normally one day and failing the next
Other body functions (windows, locks, lighting) may also act up if a shared connector is involved
Engine performance and drivability remain unaffected in most cases

What Causes B1737?

Faulty mirror adjustment switch — the switch contacts wear out or accumulate debris, breaking the signal path
Damaged wiring in the door jamb — the door hinge area flexes constantly; wires fatigue and break over time
Failed mirror motor — the internal motor windings short or open, drawing too much or too little current
Blown fuse or faulty relay — loss of power to the mirror circuit prevents operation entirely
Corroded or loose electrical connectors — moisture intrusion at the mirror or door harness plug causes poor contact
Body control module malfunction — the BCM itself may misinterpret switch inputs due to internal circuit failure
Chafed wiring in wet areas — water exposure accelerates insulation breakdown

How to Diagnose B1737

Connect an OBD2 scanner and confirm B1737 is stored, then record the freeze-frame data before clearing anything—this shows what the engine was doing when the fault appeared.
Check for related trouble codes in the B-body series; codes like B1700–B1705 often share common ground or power circuits, and addressing the root cause of one may clear the others.
Perform a visual inspection of the mirror switch, its wiring, and the door harness at the hinge point where flexing causes wires to break first; look for cracked insulation, green corrosion, or disconnected plugs.
Operate the mirror switch while monitoring live data on the scanner (if supported) or using a multimeter to verify voltage present at the motor connector when the switch is pressed.
Test the switch itself for continuity across its contacts using a multimeter—replace if resistance is out of spec or readings are erratic.
Clear B1737, complete a full drive cycle that recreates the freeze-frame conditions, and verify the code does not return before considering the repair complete.

Repair Options and Costs

Switch replacement: If the mirror adjustment switch itself has failed, a new unit typically runs $120–$450 depending on your vehicle and whether you use OEM or aftermarket parts.

Wiring or connector repair: Damaged wires or corroded plugs can often be repaired for $80–$250, depending on whether you need to splice sections or replace entire harness connectors.

Body control module replacement: If diagnostics point to a faulty BCM, expect to pay $300–$900 for repair or replacement plus programming costs at a dealership or qualified shop.

How Much Does It Cost to Fix B1737?

Total repair costs for B1737 range from approximately $80 to $900, with the final figure depending entirely on which component is actually at fault. The switch is the most common culprit and also the least expensive to fix. Wiring repairs fall in the middle range. BCM replacement is the costliest scenario but is rarely the root cause. An accurate diagnosis before purchasing parts will almost always save money, so check the cheap fixes first—fuses, switches, and visible wire damage—before committing to expensive module replacement.

Can You Drive with B1737?

B1737 is classified as a short-term severity issue, meaning it generally poses no immediate risk to drivability. The mirror simply will not adjust horizontally, which is inconvenient but not dangerous. That said, if the malfunction involves exterior lighting or wipers, or if the issue extends to central locking and leaves the vehicle unsecured, address it more urgently. Otherwise, you can continue driving while you schedule a repair.