[NZ Jonny]

Hi Andrew,

I remember working on a nox sensor fault on a early model 508 back in the day - and am unsure if it was the same engine as yours, and it's highly likely its not the same issue... But worth checking.

I remember when I removed the sensor, it was completely caked in carbon from the exhaust. The sensor itself has a shell with small holes to allow entry of exhaust gasses for measurement,

A google search example:

And if these holes are blocked then the sensor cannot read the nox levels, and based on its abnormal readings because of this, the engine ECU thinks the sensor is faulty and triggers the fault code.

I haven't worked at Peugeot for many years now so I'm unsure if this is common problem nowadays, or if it was just a one off fault on an early model. But yeah, if you can remove the sensor yourself, it's worth a look.

And you should look into getting an ECU scanner, you can get them fairly cheaply from any auto store. Then Delete the fault code yourself - as it could only be intermittent, and may only fault under certain conditions.

Hope this helps anyway,


John