A device and method for determining the status of an anti-lock brake system in a tractor-trailer configuration. The device includes a connector that can be connected to the trailer or tractor separately or connected to both the trailer and tractor simultaneously. Once connected the device begins to operate self-sufficiently by monitoring the data transmissions in a communication medium. Initially from monitoring the data transmission, the device detects whether it is attached to the trailer, tractor or both. From this determination, it either continues to monitor or proceeds to transmit data.