Depollution Fault

[cjgos 0]

Hi all, newbie C4 owner here. I picked up my new (2004) C4 2.0 HDi VTS yesterday. All was well on the hour drive home across country, but I then noticed the engine warning light and Depollution Fault message (with no other obvious symptoms). I've never owned a Citroen before and so it's not something I've come across before. I have looked at other threads on the topic and there appears to be a range of non-definitive causes and not many solutions, so a few questions - 

1) Is it a serious fault? i.e. will it stop me driving the car? 

2) Has anyone discovered the cause of the fault and rectified it effectively? 

3) Does it need main dealer input? 

 

Thanks in advance. 

[paul.h 319]

You need to use a code reader to see what fault code has been generated when the engine management light came on. It could be anything that affects the exhaust emissions but without the fault code you could end up replacing lots of parts until you get to the one that has a fault. However, have a look for anything obvious such as an air leak on the inlet ducting or a loose electrical connector. With the light on you might find the engine performance is reduced and limited to 3000 rpm. It will be ok to use for now but needs sorting. It is possible the car had the fault when you got it but the code was deleted so the warning went off and then came back on when driving back - if so it might be something expensive and the previous owner did not want to fix it. If the car was bought from a dealer then it should be sorted by the dealer.

You could pay a garage for a diagnostic check but it is cheaper to buy a code reader and do it yourself. If you do, one that gives some live data is a bit dearer but is more useful and as an example from Gendan for £34.94 https://www.gendan.co.uk/product_FXNT200.html

[cjgos 0]

Thanks Paul, I suspect you might be correct about the previous owner as the ash tray covering the OBD was only loosely refitted! I have a basic code reader from Euro Parts, so I'll give that a go first. 

 

[cjgos 0]

On 11/15/2021 at 9:32 PM, paul.h said:

You need to use a code reader to see what fault code has been generated when the engine management light came on. It could be anything that affects the exhaust emissions but without the fault code you could end up replacing lots of parts until you get to the one that has a fault. However, have a look for anything obvious such as an air leak on the inlet ducting or a loose electrical connector. With the light on you might find the engine performance is reduced and limited to 3000 rpm. It will be ok to use for now but needs sorting. It is possible the car had the fault when you got it but the code was deleted so the warning went off and then came back on when driving back - if so it might be something expensive and the previous owner did not want to fix it. If the car was bought from a dealer then it should be sorted by the dealer.

You could pay a garage for a diagnostic check but it is cheaper to buy a code reader and do it yourself. If you do, one that gives some live data is a bit dearer but is more useful and as an example from Gendan for £34.94 https://www.gendan.co.uk/product_FXNT200.html

Got my Gendan yesterday and the fault code is P2565 - Turbo Charge Boost Control Position Sensor A Circuit High. 

 

It reset ok, but was back this morning. 

[paul.h 319]

I am not sure but possibilities for this could include the turbo vanes sticking or the pressure sensor giving a wrong value. To test might need the boost pressure given by the sensor being checked with a pressure gauge mounted in the same place. I am not sure where the sensor might be but it could be a MAP sensor on the inlet manifold. If you find it see if it is blocked with oil. If your code reader gives live data see what pressure is being shown and how it changes as you accelerate and at what value the engine management light comes on.