Excellent, that is good news. Now you know exactly what type of problem to look for, and where to look for it.
A circuit fault is usually an easy problem to fix. This is most likely a problem with the wiring harness or with the sensor. I.e. a broken or shorted connection, either in the wiring to the sensor or in the sensor itself. Cleaning of the sensor or its tone ring won't help unfortunately, since the code reflects that the diagnostics found an issue with the actual electrical structure of the circuit, not with its performance or readings.
The theoretical next step for troubleshooting would be to test the wiring harness from the control unit to the wheel sensor for continuity and shorts. However, another option would be to just replace the sensor straight away. There is a pretty good (not guaranteed, but good) chance that that will fix the problem in this particular situation. And they are so cheap and easy to replace that you may as well begin there.
Here is a search on UK Ebay by the part number (Volvo P/N 3515092) that shows many results for around 20 GBP.
https://www.ebay.co.uk/sch/i.html?_f...15092&_sacat=0
You could probably get one for very cheap from a breakers also. Or if you want to do more diagnostics before buying anything, you also could try swapping the sensors from the left front to the right front and vice versa, then check for codes again and see if it gives you a new code showing that the fault moved to the opposite side.
But simplest route, I would just give a new one a try and see if that solves it. You may also need to go through the procedure to erase the fault codes in the ABS computer after replacing the sensor to confirm that the fault has gone away and doesn't return.
Let us know how it goes!