OBD-II Fault Code

B1794: Lamp Headlamp Low-Beam Circuit Failure

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for B1794.

System family

Body

Manufacturer-specific

Repair category

Lighting

Use this category to narrow your checks before replacing parts.

Severity

Medium

Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.

What B1794 usually means

Lamp Headlamp Low-Beam Circuit Failure.

Common symptoms

Body/accessory warning lamp or feature not working

Likely causes

Blown bulb/LED module; Poor ground; Fuse/relay fault; Switch/module/wiring issue; Low signal voltage; Weak power supply; High resistance/poor ground; Failed sensor

Diagnostic checks

Check related fuses, connectors, grounds and switch/module power supply; Check bulb/module, fuse, ground and connector corrosion; Check sensor reference voltage, ground and signal voltage

Repair guidance

Replace failed bulb/module, repair ground/wiring, replace switch/relay if confirmed; Repair poor ground/power feed or replace confirmed faulty sensor

Verification after repair

Operate the affected body/accessory system and rescan

Note: Confirm vehicle make/model/year because manufacturer-specific codes can vary; Manufacturer-specific: confirm definition and test steps in the vehicle service manual. A DTC identifies a circuit or system condition, not always the failed part.