B1793 — Autolamp Sensor Input Circuit Short To Ground

B1793 — Autolamp Sensor Input Circuit Short To Ground. A fault in the body electrical system. The car is usually drivable while you plan the repair. Typical causes: damaged wiring in door jambs or wet areas, faulty switch, motor or actuator of the affected system, 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 B1793 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 B1793 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1793 (parts and labor, USD, independent shop rates): Repair wiring or connectors: $80–$250; BCM repair or replacement: $300–$900; Replace the switch or actuator: $120–$450. Overall, fixing B1793 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 B1793 mean?

How much does it cost to fix B1793?

Repair wiring or connectors — $80–$250; BCM repair or replacement — $300–$900; 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 B1793 myself?

Start with a scan: confirm B1793, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the body electrical system, and verify the suspect component against live data before buying parts.

What is the most common cause of B1793?

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

Is it safe to drive with B1793?

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 computer detects that a sensor input is permanently shorted to ground instead of receiving the expected voltage signal, it logs trouble code B1793. Specifically, this code refers to the Autolamp Sensor Input Circuit Short To Ground condition. The autolamp system relies on a photosensor—usually mounted near the rearview mirror or on the dashboard—to monitor ambient light levels and automatically switch the headlights on or off accordingly. When the wiring or connector feeding this sensor develops a short to ground, the body control module receives an invalid signal and sets B1793 once the fault is confirmed under the specified operating conditions.

Unlike powertrain codes that often trigger immediate drivability concerns, B1793 lives in the body electrical category. The module does not set this code based on a single glitch; it requires repeated detection of the abnormal circuit condition before illuminating the check engine or body system warning light. When technicians retrieve this code, the accompanying freeze frame data reveals engine load, RPM, coolant temperature, and vehicle speed at the exact moment the fault was recorded. Reproducing those conditions during testing is essential for accurate diagnosis.

Symptoms of B1793

In most cases, engine performance and drivability remain completely unaffected
The automatic headlight function fails to operate, or headlights stay on or off at inappropriate times
Interior lighting, power locks, power windows, or windshield wipers may function intermittently or stop working entirely, depending on which circuits share the affected wiring
The body system or check engine warning light illuminates on the instrument cluster
In rare cases involving shared BCM circuits, multiple unrelated features may display erratic behavior simultaneously

Common Causes of B1793

Corroded, dirty, or loose electrical connectors at the autolamp sensor or along the harness
Damaged insulation or broken wires in high-flex areas such as door jambs, tailgate hinges, or wire passages through the firewall
Faulty autolamp photosensor or associated switches and actuators in the affected circuit
Body control module (BCM) internal failure or software corruption
Blown fuse, triggered fusible link, or failed relay feeding the autolamp circuit

How to Diagnose B1793

Connect an OBD2 scanner compatible with body codes, retrieve all stored codes, and record the freeze frame data associated with B1793. Note the exact vehicle conditions when the fault occurred.
Investigate any related diagnostic trouble codes present alongside B1793—these often point to the underlying cause. Also search manufacturer technical service bulletins for your specific make, model, and model year; many body electrical issues have documented factory fixes or software updates available.
Perform a thorough visual inspection of the autolamp sensor harness and connectors. Look for chafed wiring, broken strands hidden under tape, corrosion buildup, or pins that are pushed out or bent.
Access live data and operate the suspected faulty function—autolamps, locks, windows—while monitoring the relevant switch and motor PIDs to see whether the module receives proper input signals.
Pay special attention to flex points where wires pass through door jambs or around hinges. These areas experience constant movement and fail more frequently than stationary sections of harness.
After repairs, clear the code, complete a full drive cycle that reproduces the conditions captured in the freeze frame, then re-scan to confirm B1793 does not return.

Repair Options and Costs

Depending on what the diagnosis reveals, several repair paths address B1793:

Wiring repair or connector replacement: Damage in the harness or corroded connector terminals often cause this code. Soldering, heat-shrinking, or replacing the affected connector typically runs $80–$250 including labor.
Body control module (BCM) repair or replacement: If the BCM itself has failed internally, repair or unit replacement plus programming ranges from $300–$900 depending on whether a rebuilt or new module is used.
Autolamp sensor or switch replacement: When the photosensor or an associated switch or actuator is the faulty component, parts and labor generally total $120–$450.

Overall, fixing B1793 typically costs between $80 and $900. The widest range reflects the variety of components that can trigger this code. Always complete proper diagnosis before purchasing parts—an accurate assessment prevents spending on expensive modules when simple wiring repair is the real solution.

Can You Drive with B1793?

This code is classified as short severity—body electrical faults rarely impair engine operation or transmission function. Most vehicles remain fully drivable. However, safety implications exist if the autolamp system controls exterior lighting or if the fault involves central locking. Driving at night or in poor weather without automatic headlights presents a hazard, and a malfunctioning central locking system can leave the vehicle unsecured. Until the root cause is identified and repaired, exercise extra caution and avoid relying on automatic lighting functions.