What Does B1796 Mean?
This code indicates the Body Control Module (BCM) has detected an unintended voltage supply (short to battery voltage) in the low-beam headlamp circuit. The BCM monitors the headlamp circuit and has identified that battery voltage is present on the control side of the circuit when it should not be, typically when the lights are commanded off. This creates an overload condition and prevents proper headlamp operation.
Common Causes
45%
Damaged or chafed wiring harness causing direct short to power wire in headlamp circuit
25%
Faulty headlamp bulb socket with internal short to battery voltage
20%
Failed headlamp relay stuck in closed position providing constant power
10%
Body Control Module internal driver circuit failure
Diagnostic Steps
1
Step 1: Perform visual inspection of low-beam headlamp bulbs, sockets, and wiring harness for obvious damage, melting, corrosion, or chafing against metal components. Pay special attention to areas where harness passes through firewall or near sharp edges.
2
Step 2: Disconnect the low-beam headlamp connector at the bulb socket. Using a digital multimeter, check for battery voltage (12V+) on the BCM control wire with ignition on and headlamp switch off. Voltage present confirms short is upstream of socket.
3
Step 3: Locate and remove the headlamp relay (if equipped). Check for battery voltage at the relay control terminal from BCM. If voltage disappears at bulb connector after relay removal, replace relay. If voltage remains, proceed to next step.
4
Step 4: Disconnect BCM connector controlling headlamp circuit. Measure resistance between the headlamp control wire and battery positive at the harness side. Reading below 10 ohms indicates direct short in harness between BCM and headlamp. Reading of OL (open/infinite) indicates BCM internal fault.
5
Step 5: If harness short is confirmed, trace wiring using wiring diagram and physically inspect/repair damaged section. Use electrical tape and protective conduit on repaired sections.
6
Step 6: After repair, reconnect all components, clear code, and perform functional test cycling headlamps on/off multiple times. Monitor for code return and verify proper headlamp operation with no overheating at repair location.
Estimated Repair Cost
$100 - $650
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an unintended voltage supply (short to battery voltage) in the low-beam headlamp circuit. The BCM monitors the headlamp circuit and has identified that battery voltage is present on the control side of the circuit when it should not be, ...
The most common cause of B1796 (Lamp Headlamp Low-Beam Circuit Short To Battery) is: Damaged or chafed wiring harness causing direct short to power wire in headlamp circuit
Typical repair costs for B1796 range from $100 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may have inoperative low-beam headlamps reducing nighttime visibility and making the vehicle unsafe for night driving. The short circuit condition can also drain the battery and potentially cause wire overheating or fire risk. Repair should be completed before operating vehicle after dark.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1796 to identify the root cause.
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Quick Info
Category
Body
System
Exterior Lighting System
Difficulty
Type
Manufacturer
Recommended Tools
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