peugeot 407 keeps displaying inaccurate messages ?

Just thought, might be loose connection to one of the lights, when moving, opens up, but when you check, all ok. check all the plugs wires etc on the light clusters.

SD
October 2011

Depends on how much you want to spend.

Could be the sensor, usually sensing the current drawn, so if a light bulb out, not as much current drawn, so it says faulty lamp. or could be the engine control unit.
ECU very expensive.
Cheapest solution. Ignore it.
Just check them every so often, I use the reflection on the vehicle behind to check mine on a regular basis

SD
October 2011