GLA Hybrid Tire Pressure ABS and Steering Issues

Sounds like a pain! I have a GLA as well and experienced something similar last year. If you're seeing the ABS light and feeling vibrations, plus the steering is heavy, it definitely points to a pressure loss in one of your tires affecting the tire monitoring system. The tire monitoring system relies on sensors in each wheel to measure air pressure. When a tire's pressure drops significantly, it can trigger all sorts of warnings. Have you checked the tire itself for any visible damage, like a nail or screw? A slow leak from a valve can also cause these issues. A punctured tire can cause pressure loss, but a defective valve can cause this as well.

I did a quick visual check, but didn't spot anything obvious. What exactly do you mean by 'a slow leak from a valve'? Is that something I can easily check myself, or is it best left to a professional?

By 'slow leak from a valve,' I mean the valve stem—the part you attach the tire gauge to—might not be sealing properly. Sometimes, they get a bit corroded or the core inside gets loose. You could try tightening the valve core with a valve core tool (they're cheap), but honestly, if you're seeing all those symptoms, and especially if you suspect a puncture, it's probably best to get it checked out by a tire place. They can properly inspect for punctures and test the valve. Continuing to drive with a significantly low tire could damage the tire further, or even be dangerous. So, my recommendation is to go to the workshop.

I took the GLA to a local workshop. Turns out it was indeed a defective valve in the tire, causing the slow leak and triggering all the warnings. They replaced the valve, re-inflated the tire, and reset the tire monitoring system. The total repair cost was 280€. Everything is back to normal now! I really appreciate you sharing your experience!