SQ5 Power Steering & ABS Issues Tied to Tire Pressure

As someone with some experience working on cars, I had a very similar issue with my 2015 S4. The symptoms you describe match exactly what I encountered, tire pressure warning, ABS light, and steering problems all happening together. The root cause turned out to be a defective tire pressure sensor valve that was causing a slow air leak. The pressure loss was significant enough to trigger multiple warning systems. The uneven tire pressure made the ABS system think there were traction issues, which then affected the power steering assistance. The repair cost me 280 Euro including diagnosis, valve replacement, and system reset. After fixing the punctured tire valve, all warning lights cleared and the steering returned to normal. To help troubleshoot your specific case better, could you share: Current tire pressures on all wheels, Whether the tire pressure warning is constant or intermittent, If you notice the symptoms more during specific conditions (cold starts, high speeds, etc), When you last had your tires rotated or balanced A faulty tire sensor can sometimes give false readings, but given the steering vibrations, there might be an actual pressure issue that needs addressing. Best to have it checked before it leads to more serious problems.

Thanks for the reply. Latest service was done at 62000 KM about 4 months ago. I checked the tire pressures manually and found the front right tire at 1.8 bar while others are at 2.4 bar. The low tire pressure warning is constant, not intermittent. Steering vibrations are worse during highway speeds. Cold starts seem normal. The air leak seems slow but consistent, I had to refill the problematic tire twice this week. Found a small nail near the shoulder area, which explains the punctured tire situation. Will get it patched or replaced based on the mechanic's assessment. Good call about the tire sensor connection to other warning systems. Your experience really helps confirm my suspicion that a single tire issue could trigger multiple warnings.

Thanks for the pressure readings, that significant difference between your front right tire (1.8 bar) and the others (2.4 bar) matches the pattern I saw in my S4 case. The nail location near the shoulder makes repair trickier than if it were in the center tread. When I used a proper tire gauge to track my pressure loss, it dropped about 0.2 bar per day, similar to your situation. The tire monitoring system in these models is quite sensitive and will trigger multiple warnings when pressure differences exceed 0.5 bar between wheels. Since you mentioned highway speed vibrations, definitely avoid high speeds until fixed. In my case, the uneven pressures eventually damaged the tire sidewall because I drove too long before addressing it. For reference, correct tire pressures should be: Front: 2.4 bar (cold) Rear: 2.4 bar (cold) Given the shoulder damage and consistent pressure loss, you might be looking at a replacement rather than a patch. My mechanic explained that shoulder repairs often fail due to the flexing in that area. The entire repair including new tire cost me 320 Euro.

Looking at the pressure readings posted really helped clarify things. Manually checking confirmed a significant pressure drop in the front right tire at 1.8 bar while other tires maintain 2.4 bar. This constant flat tire situation, combined with the nail near the shoulder, explains the multiple warning systems activating. The tire monitoring system is clearly doing its job detecting the pressure loss. Having to refill twice in one week shows its not just a sensor malfunction but a real air leak. The steering vibrations getting worse at highway speeds makes total sense with the uneven tire pressures. Will keep the appointment for next week but feeling more confident about the diagnosis. Based on the shared experience, expecting either a tire replacement or possibly sensor work, rather than a more complex steering or ABS system repair. Good to know these systems are interconnected and a single tire issue can trigger multiple warnings. Hope the repair costs stay around the 320 Euro mark mentioned. The shoulder location of the nail probably means replacement rather than patching, but better that than risking a blowout at highway speeds. Will update once the mechanic takes a look.