Renault Modus ABS and Steering Issues

That is quite a confluence of issues. I experienced something similar with my 2017 Opel Astra. The low tire pressure warning can trigger a cascade of electronic errors. Have you inspected the tires closely for any punctures, however small? Even a slow leak can cause the tire pressure to drop gradually, which could affect the ABS and power steering systems due to their reliance on wheel speed sensors. Also, have you tried resetting the tire pressure monitoring system?

Resetting the TPMS? How do I even do that? And I did give the tires a quick look, didn't spot anything obvious like a nail or screw. Could a dodgy valve cause all this drama?

The procedure for resetting the TPMS varies by vehicle, but it usually involves navigating through the car's infotainment system or a dedicated button. Consult your owner's manual for specific instructions. And yes, a defective valve could indeed be the culprit. A slow leak from a faulty valve can gradually reduce tire pressure, leading to the symptoms you described. Given the severity of the symptoms, I recommend taking it to a qualified workshop for a thorough inspection.

Cheers for the advice! Turns out it WAS a valve problem. Tiny leak, but enough to mess everything up. 280€ later, all sorted. New valve, tire re-inflated, and all the warning lights are gone. Steering's back to normal. What a relief!