B1797: Lamp Headlamp Low-Beam Circuit Short To Ground

What does B1797 mean?

B1797 is a diagnostic trouble code indicating "Lamp Headlamp Low-Beam Circuit Short To Ground". The ECU is detecting a voltage reading that is below the expected range in the lighting circuit. This typically points to a wiring short, a faulty sensor, or a grounding issue.

Symptoms you may notice

• Check engine light (MIL) illuminated on dashboard
• Intermittent warning lights
• Erratic gauge readings

Common causes

• Damaged or corroded wiring harness
• Loose or disconnected electrical connector
• Failed lighting sensor or actuator
• Blown fuse in the related circuit
• Poor ground connection

What should you do?

This code sits in the exterior lighting. Nothing about how the car drives changes, but how easily other road users see you does, and a light out is an on-the-spot fine and an inspection failure. Worth sorting before you next drive at night.