B1604: Lamp Anti-Theft Indicator Circuit Open
MediumBodyLighting
What does B1604 mean?
B1604 is a diagnostic trouble code indicating "Lamp Anti-Theft Indicator Circuit Open". This means there is an electrical break in the lighting wiring — a connector may be unplugged, a wire broken, or a component has failed internally. The ECU detected no signal where it expected one.
Symptoms you may notice
- Check engine light (MIL) illuminated on dashboard
- Intermittent warning lights
- Erratic gauge readings
Estimated repair cost
Typical range in Australia (parts + labour)
$80 – $400 AUD
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.
Get a diagnosis for YOUR car
Code B1604 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.