B1742 — Mirror Passenger Vertical Switch Circuit Open

B1742 — Mirror Passenger Vertical 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, blown fuse or failed relay, 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 B1742 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 vertical 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 B1742 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1742 (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 B1742 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 are the symptoms of B1742?

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

Will B1742 clear itself?

Sometimes B1742 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 B1742?

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 B1742 myself?

Start with a scan: confirm B1742, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the mirror passenger vertical switch, and verify the suspect component against live data before buying parts.

Is it safe to drive with B1742?

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 vehicle's control unit logs trouble code B1742, it's telling you that the electrical pathway responsible for the passenger-side mirror's vertical adjustment has been interrupted. The term "circuit open" is the key here — it means somewhere along the path from the switch to the mirror motor, current cannot flow as the module expects it to. This isn't a mechanical failure of the mirror itself; it's an electrical break in the system that controls it.

Modern vehicles rely on the body control module (BCM) to continuously monitor switches, motors, and actuators throughout the car. When you press the passenger mirror up or down switch, the BCM expects to see a specific change in voltage or resistance. If that signal never arrives because a wire is broken, a connector is loose, or a fuse has blown, the module logs B1742 after the fault persists for the required number of drive cycles. Freeze frame data captured alongside the code records the engine speed, load, temperature, and vehicle speed at the exact moment the module first detected the problem — information that proves invaluable during diagnosis.

Understanding this code matters because the passenger mirror vertical adjustment is one small piece of your vehicle's body electrical network. While the engine will continue running normally, losing this function can be inconvenient and, depending on your mirror adjustment needs, potentially create a blind spot that affects how you position your vehicle. The good news is that B1742 rarely signals a serious problem — most causes are inexpensive to repair.

Symptoms of B1742

The most obvious sign of B1742 is that the passenger mirror fails to move vertically when you operate the switch, or it works intermittently — responding sometimes and failing other times as the electrical connection makes and breaks. A check engine light or body system warning light typically illuminates on the dashboard once the module confirms the fault. Importantly, B1742 has no effect on engine performance, transmission operation, or braking systems — your vehicle drives exactly as it should in every other respect.

Causes of B1742

The majority of B1742 faults stem from straightforward electrical problems rather than component failures. An internally open switch — where the physical contacts inside the mirror adjustment button have failed — ranks among the most frequent culprits. Corroded, unplugged, or backed-out connectors at the mirror housing or BCM cause the same symptoms, as do broken wires within the mirror harness, particularly at flex points where wiring bends through door jambs. A blown fuse protecting the circuit will also generate this code. Less commonly, the body control module itself may be faulty, sending incorrect signals or failing to process inputs properly. Failed motors or actuators within the mirror assembly, while possible, occur less frequently than wiring and connector issues.

How to Diagnose B1742

Effective diagnosis follows a logical path from simple observations to targeted electrical testing. Begin by connecting an OBD2 scanner, confirming B1742 is present, and recording all freeze frame data — this snapshot reveals exactly what conditions existed when the fault first appeared. Next, scan for any other stored trouble codes; related body codes often point toward the true root cause, such as a broader wiring problem affecting multiple circuits. Consult manufacturer technical service bulletins for your specific make and model, as some B1742 faults have known factory fixes or software updates. Perform a thorough visual inspection of the mirror harness and connectors, looking for damaged insulation, corrosion buildup, or pins that have shifted out of position. Use a multimeter to conduct continuity testing along the entire circuit length, and gently wiggle the wiring while measuring — an intermittent open will reveal itself through fluctuating readings. Monitor the switch and motor parameter IDs in live data while operating the mirror, watching for expected value changes that confirm path integrity. Finally, inspect connector locations at door hinges and body passages where wires endure repeated flexing and are most likely to fracture. After any repairs, clear the code, complete a drive cycle matching the freeze frame conditions, and verify B1742 does not return.

Repair Options and Costs

Repair costs for B1742 vary significantly depending on which component is actually at fault. Wiring harness repair or connector remediation typically runs between $80 and $250 for parts and labor at an independent shop. If the mirror adjustment switch itself has failed internally, replacement generally costs $120 to $450 depending on your vehicle's make and whether you use OEM or aftermarket components. The body control module repair or replacement represents the higher end of the spectrum, usually between $300 and $900, as it may require programming or module reflashing. Most shops will charge a diagnostic fee of $75 to $150 to perform the electrical testing that pinpoints the exact cause before proceeding with repairs.

Total repair expenses for B1742 typically fall between $80 and $900, with the lower end covering wiring fixes and the upper end addressing BCM replacement. An accurate electrical diagnosis before purchasing parts prevents unnecessary spending — the most expensive repair is rarely the first one that needs trying.

Driving Safety Verdict

B1742 carries a short-term driving safety rating, meaning your vehicle remains safe to operate in most circumstances. Body electrical codes of this type rarely impact engine performance, braking, or steering. The primary concerns arise only in specific situations: if your mirrors are critical for visibility and you cannot adjust them, or if the fault is part of a broader system issue affecting exterior lighting or wipers during adverse weather conditions. Central locking malfunctions associated with body module problems could theoretically leave a vehicle unsecured, but this is uncommon with an isolated mirror switch fault. Use reasonable judgment, prioritize getting the diagnostic done promptly, and address any safety-critical systems that share the same circuit.