It is sometimes very frustrating with modern motors which develop faults and can be difficult to repair. I trust you had the fault codes read and someone decided to renew the sensor in the exhaust as the code related to that sensor itself. I am sure you have tried a lot of things and it can get very expensive and you get no further forward. There is no point guessing but I would start by getting the fault code, try googling it,try accessing a proper Peugeot forum and asking the right people, it may be there is nothing wrong with the sensor and your motor has developed a slight misfire, it could be a wiring problem up to your ECU, these are things that would need to be looked at but it needs someone who knows what they are doing, it is easy for someone to say change this and that, it`s not their money they are guessing with. Good luck.
cdc
December 2016
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