S40 ABS and Steering Problems

Sounds like more than just low pressure. Those symptoms—ABS light, steering issues—point to something affecting the car's sensors. Is the tire pressure sensor itself possibly faulty? I'd want to rule that out before assuming the worst.

Thanks! How do I check if the tire sensor is bad? Do I need special tools, or can I do it myself?

Checking those sensors can be tricky without the right gear. Given the steering issues and ABS light, it's probably best to get it checked at a workshop. They'll have the diagnostic tools to pinpoint the exact problem. It could still be a valve issue causing a rapid pressure loss which is throwing everything off, but with those added symptoms, I'd play it safe.

You were right! The garage found a defective valve in one of the tires causing a slow leak. This messed with the ABS and power steering sensors. Cost 280€ to replace the valve and recalibrate the system. Thanks for the advice!