Recommended Trailer Brake Controller for a 2007 BMW X3 with Factory Trailer Hitch and Wiring

Question:

I want to install a brake controller in my 2007 X3. It has an OEM receiver with OEM wire harness. How do I splice in a brake controller in this situation? I have seen other similar QandAs but none of them address the situation when the OEM hitch kit with wiring is already installed.

asked by: Andy

Expert Reply:

If your 2007 BMW X3 has a factory 7-way trailer connector and you want to install a brake controller like the Prodigy P3 # 90195 you'll just need to hard wire the controller in. To do so the black wire from the P3 will be connected to the BMW's battery through a circuit breaker and the white wire needs to be grounded. You can use our # 5506 kit to make the connections. The blue wire from the controller is connected to the brake circuit that runs back to the 7-way which you can use # 10-1-1 for. The red wire connects to the cold side of the stop light switch.

The correct stop light switch only shows power when the brake pedal is pressed. This circuit can be difficult to find on a BMW like yours but you may be able to use any dedicated brake light circuit. This can also be difficult to find because the X3 has multiplex wiring so the brake light circuits themselves have other functions and are not an option.

This is why we often recommend using a wireless brake controller like the Curt Echo, part # C51180, for BMWs since it only needs a 7-way connector with an active 12 volt circuit to function. It plugs inline with the 7-way connector and is controlled by your smartphone. I've attached a video for you.

If the X3 has a 4-way connector and not a 7-way you need to add a 7-way using our # ETBC7 kit. This includes everything needed to convert your 4-way and have a fully functioning 7-way connector.