If you are looking at a schematic, and the relay supplies only the ABS, then pulling the relay should be equivalent.

If there is a ABS sensor fault, the rear one will not likely affect only one front wheel; it would affect overall front/rear balance. The sensors are very simple devices; a magnet with a coil wrapped around it. As a tooth passes the magnet the magnetic field is altered, and that change in the magnetic field induces a current in the coil. the current is sensed by the control unit. Sensor faults are usually in the leads, rather than in the coil.
Electrical continuity of the assembly can be checked with an ohmmeter, and wiggleing/pulling the leads.

There is a used rear on Ebay for $19.99