BMW X6 License Plate Lights Out: Mouse Damage, a Shorted Harness and a Body Module Fault
A 2021 BMW X6 came in with the rear license plate lights not working — and it turned into an unexpected repair. The cause was again a mouse nest. The chewed harness had shorted, and the body control module set a hard fault and stopped switching the lights on. We traced and repaired the harness, then restored the module with a software update.
2021 BMW X6 October 23, 2026 4 min readDocumented by Alex
How it arrived
Driven in with the rear license plate lights not working.
Reported symptoms
Rear license plate lights not working
Outcome
The mouse-chewed harness on the X6 was repaired, a software update on the body control module cleared its hard fault, and the rear license plate lights work again. The work carries our 12-month / 12,000-mile warranty on new parts, whichever comes first.
This 2021 BMW X6 came in for what looked like a small job: the rear license plate lights were not working. It turned into an unexpected repair — and, like the Tesla Model Y we wrote about, the cause was a mouse nest.
Tracing the circuit
On a modern BMW the lights are not simply wired to a switch. The body control module switches them, watches the circuit, and shuts an output down if it sees a fault. So the job was to follow the circuit from the module to the lights, which meant taking the trim out of the cargo area and opening up the wiring along the way.
The cargo area opened up to follow the harness toward the rear of the car.Behind the side trim: the rear fuse box and the harnesses running to the back of the car.
What we found
The mice had nested in the car and chewed through the harness. With the insulation gone, the wires had shorted. The body control module did exactly what it is designed to do: it saw the short, set a hard fault, and stopped activating the lights to protect the circuit.
Repairing the harness: multimeter on the circuit, solder and heat-shrink on the seat.
The repair — and why the wiring alone was not enough
We repaired the broken harness, soldering and sealing the damaged wires and protecting the section again. But with the wiring fixed, the lights still stayed off: the module was holding on to its hard fault. A software update on the body control module cleared that state and restored the lights.
Both license plate lights working again. (Plate blurred.)
What to take from this
A dead bulb-type light on a modern car is not always a bulb. When the module has shut the circuit down, the repair is the wiring and the module — which takes the right diagnostic and programming tools. More on our electrical diagnostics, module programming, and our BMW service page.
From the job
What we photographed
Tracing the harness through the cargo area.Repairing the harness.License plate lights restored.
FAQ
Questions this job raises
Why are the license plate lights on my BMW not working?
It can be a bulb or LED, but on this 2021 BMW X6 it was a harness chewed by mice. The damaged wires shorted and the body control module shut the lights off.
Why did the lights stay off after the wiring was repaired?
The body control module had stored a hard fault from the short and kept the output disabled. A software update on the module restored it.
Can mice damage a BMW’s wiring?
Yes. Mice nest in parked cars and chew wiring insulation. On this X6 the chewed harness shorted and disabled the license plate lights.
Can a body control module be fixed without replacing it?
Often, yes. On this X6, once the wiring was repaired, a software update brought the module back without replacing it.
Do you repair BMW electrical problems in Worcester?
Yes. We diagnose and repair BMW wiring and module faults, including programming, at our Worcester, MA shop.
