The speedometer dips to 0 and then jumps back to the correct speed; this has happened three times while I've had the car. This is a relatively common fault with the speed sensor on the gearbox on both the Peugeot 406 and the Citroën Xantia, with which it shared its platform.
High oil usage, especially when driven hard. Nearly 1 litre in 4000km. Even when new, this is a particular trait of the 2.2 petrol engine, due to high PCV pressure.
Other than that, nothing apart from the expected wear and tear on a 12-year old car.
A real driver comfort-oriented tourer, with long service intervals (1 year/30,000km) and extremely competent handling.
The 2.2 petrol engine is a bit thirsty by modern standards (8.7l/100km), but it's also smooth, has good torque and makes a great noise.
The gearbox is serviceable, but not the best I've used. Throws are rather long and the synchros can be a bit sluggish on downshifts, especially when cold. Ratios are good for a 5-speed box, with 130km/h corresponding to 3300rpm.
The TS trim level trades a bit of comfort for a stiffer setup that pays dividends in the corners. Only the Mondeo from the same era could match it for price/handling ratio, and it's still among the best today. The high-speed ride is very comfortable and the car gently smooths out bumpy motorway or highway surfaces.
Interior quality is solid and well built, instruments are clear and easily readable, and the multifunction display has the most important information at a glance. Buttons and switchgear have a very plasticky feeling to them, though.
The stock Clarion stereo has great sound and supports an optional CD changer. I've added an AUX input to the CD changer port instead so I can use my MP3 player. The adapter is cheap, and any Peugeot dealer should be able to unlock the CD changer functionality in a couple of minutes.
Seats are comfortable and have a large range of adjustment. Huge amounts of space in the back seat as well; the 406 seats 5 adults no problem.