Peugeot 806 Tire Pressure Warning

Sounds like a classic sensor issue. Those things have batteries that don't last forever. How old are the sensors? Have you tried resetting the system after manually inflating the tires? Sometimes a simple reset does the trick, but honestly, with those symptoms, I'd bet on a dead sensor battery.

I haven't replaced the sensors since I bought the car used a few years ago, so they could be original. How do I reset the system? Is there a specific procedure for the Peugeot 806?

Yeah, if they're that old, the batteries are almost certainly done for. The reset procedure varies, but it usually involves navigating through the car's menu using the buttons on the dash or steering wheel. Check your owner's manual. But honestly, even if you manage to reset it, the error will probably come back soon. I'd recommend going to a workshop and getting the sensors checked. It will save you time in the long run.

Thanks for the advice. I took it to a workshop, and you were right – the sensor batteries were dead. Replaced all four sensors; cost me around 280€. Problem solved.