B1402 — Driver Power Window Down Switch Circuit Failure

B1402 — Driver Power Window Down Switch Circuit Failure. A fault in the body electrical system. The car is usually drivable while you plan the repair. Typical causes: blown fuse or failed relay, faulty switch, motor or actuator of the affected system, 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 B1402 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 B1402 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1402 (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 B1402 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 B1402 mean?

Is it safe to drive with B1402?

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.

Will B1402 clear itself?

Sometimes B1402 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 B1402?

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.

What is the most common cause of B1402?

The most common causes are: blown fuse or failed relay, faulty switch, motor or actuator of the affected system, damaged wiring in door jambs or wet areas.

When the engine control unit detects a problem within the body electrical architecture, it logs a specific fault code to flag the issue for diagnosis. Code B1402 specifically points to a failure in the driver power window down switch circuit — essentially, the circuit that tells the window motor to lower the driver's side window has gone outside its normal operating parameters. This code lives in the B-series family, which covers body and chassis electrical systems rather than powertrain functions.

The control module watches this circuit constantly while the vehicle runs. It expects to see specific voltage patterns whenever you press the window switch. When those readings stray outside the acceptable window for enough consecutive drive cycles — the exact number varies by manufacturer — the module stores B1402 and illuminates the malfunction indicator. The freeze frame data captured alongside the code is valuable: it records rpm, engine load, coolant temperature, and vehicle speed at the precise moment the fault occurred, giving you the best starting point for recreating the failure condition.

What makes this code common is the environment it operates in. The driver window switch endures heavy use, and its wiring runs through the door jamb — one of the harshest areas on any vehicle, constantly flexing as the door opens and closes while exposed to moisture, dirt, and temperature swings. That combination eventually takes a toll on connectors and wire insulation.

Symptoms

Check engine or warning light may or may not illuminate
Driver window fails to respond when you press the down button
Window operates intermittently, working some days and not others
Other body functions (power locks, mirrors, interior lighting) may behave erratically if a shared ground or module is involved
No effect on engine performance, transmission operation, or braking systems

Causes

Corroded or loose electrical connectors at the switch or window motor
Broken or chafed wiring within the driver door boot, where wires flex constantly
Faulty body control module unable to process switch inputs correctly
Blown fuse or failed relay supplying power to the window circuit
Defective window switch itself, internal contacts worn or contaminated
Water intrusion into the door panel damaging connectors or wire harness
Poor ground connection affecting the entire circuit

How to Diagnose

Plug in an OBD2 scanner, retrieve B1402, and record the freeze frame data before clearing it — those saved conditions tell you exactly what车速, temperature, and load were present when the failure triggered.
Pull all stored codes from every module. Codes in nearby systems often point to the real culprit; for instance, codes for both window up and down failures usually indicate a module or power supply issue rather than the switch itself.
Check manufacturer TSB databases using your VIN. Many B1402 complaints have documented factory fixes, software calibrations, or known defect patterns specific to your year and model.
Wiggle-test the wiring harness at the driver door hinge while monitoring live data on the scanner — if the window responds to flexing the wires, you've found a broken conductor inside the insulation.
Test switch operation directly with a multimeter: the switch should show continuity in one position and an open circuit in the other; resistance readings above a few ohms indicate worn contacts.
Verify power and ground at the window motor connector with the key on and switch pressed, narrowing the problem to either the supply side or the motor itself.

Repair Options

Body control module replacement or repair: $300–$900
Wiring harness repair or connector replacement: $80–$250
Driver window switch replacement: $120–$450

Total Cost to Fix

The wide price range reflects how differently this code can be resolved depending on root cause. A simple connector cleanup or replacing a corroded spade terminal might run just eighty dollars in parts. A full body control module replacement with programming and labor pushes toward the nine-hundred-dollar ceiling. The most common scenario lands somewhere in the middle once the technician pinpoints whether the fault lies in the switch, the wiring, or the module itself.

Driving Safety Verdict

Short distances are fine. Body electrical faults like B1402 do not typically compromise engine operation, steering, or brakes. However, if the driver window fails completely, visibility through that pane becomes impaired until repaired, and central locking failures in some vehicles can leave doors unlocked — both worth addressing before a long trip or bad weather.