What Does B1794 Mean?
This code indicates the Body Control Module (BCM) has detected an electrical fault in the low-beam headlamp circuit. The BCM monitors the circuit for opens, shorts to ground, shorts to power, or excessive current draw that would prevent proper low-beam headlamp operation. This is a manufacturer-specific body code, so exact diagnostic criteria may vary between vehicle makes.
Common Causes
40%
Burned out low-beam headlamp bulb or poor bulb socket connection with corrosion
30%
Damaged wiring harness or corroded connectors in the low-beam circuit between BCM and headlamp
20%
Faulty headlamp relay or internal BCM driver circuit failure
10%
Blown fuse or poor fuse box connections for the low-beam circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of the low-beam headlamp bulb and socket for obvious damage, burn marks, or moisture intrusion. Check bulb filament integrity and socket pin condition for corrosion or melting.
2
Step 2: Using a digital multimeter, check for battery voltage at the headlamp connector with headlamps commanded on. Verify ground integrity by measuring resistance to chassis ground (should be less than 0.5 ohms).
3
Step 3: Inspect the low-beam headlamp fuse in the fuse box and relay (if equipped). Test fuse continuity with multimeter and verify relay operation by listening for click and measuring coil and contact resistance.
4
Step 4: Check wiring harness between BCM and headlamp assembly for chafing, pinching, or damage. Pay special attention to areas where harness passes through grommets or near moving components.
5
Step 5: If all external components test good, use scan tool bidirectional controls to command low-beam on/off while monitoring circuit voltage. Compare left and right side circuits to identify asymmetric behavior indicating BCM driver issue.
6
Step 6: After repairs, clear codes, cycle headlamps multiple times, and road test. Verify code does not return and both low-beam headlamps operate normally under all conditions.
Estimated Repair Cost
$75 - $600
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an electrical fault in the low-beam headlamp circuit. The BCM monitors the circuit for opens, shorts to ground, shorts to power, or excessive current draw that would prevent proper low-beam headlamp operation. This is a manufacturer-spec...
The most common cause of B1794 (Lamp Headlamp Low-Beam Circuit Failure) is: Burned out low-beam headlamp bulb or poor bulb socket connection with corrosion
Typical repair costs for B1794 range from $75 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Reduced nighttime visibility creates significant safety risk for the driver and other road users. Vehicle should not be driven at night until repaired; drive during daylight only if necessary and repair as soon as possible.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1794 to identify the root cause.
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Quick Info
Category
Body
System
Exterior Lighting System
Difficulty
Type
Manufacturer
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