[Craig83]

I have an ABS fault on 2011 318d
The codes been read as

Dynamic Stability Control (DSC), Left rear wheel speed sensor, supply.

I've change the speed sensor and it's still the same I was going to get the reluctor ring changed but am curious what the supply part of the error was referring to? Any help appreciated.

[Jturbo_M3]

Since you have already replaced the speed sensor itself, you should also consider checking the entire sensor circuit, including the wiring and connections. Also, make sure that the sensor has a good ground connection as a poor ground connection can also affect the sensor.