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C8 Anti Pollution Fault

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Hi to all      My car is 2004 C8 2lt petrol
                  Well here I am in the South of France on holiday and yesterday I got a warning message anti pollution fault and the warning light on the dash, This came on at start up first thing in the morning the car is still driving very well no signs of limp mode or anything. I have noticed that I have a slight exhaust rattle at idle just lift off idle and it goes away I was meaning to check that today anyway.
What can I check myself sensors etc. I don't want to use a garage here if poss they are very expensive here in France
I have had my car for many years and It does the journey four times a year, apart from the usual brake checks and oil services which I do every trip the car has been Brill.
I hope someone can help Cheers and thank you


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It could be anything that can affect the exhaust emissions. Without using a code reader it is not possible to know what could be wrong and you could try replacing lots of parts before finding the fault. It could be one of the engine sensors or parts such as cam shaft sensor, exhaust lambda sensor, exhaust catalyst, exhaust leak affecting the lambda sensors reading, spark plug, ignition coil, air flow meter, air temperature, fuel injector, air leak between the air flow meter and manifold, air leak on one of the sensor pipes, egr valve, etc.


Without a code reader all you can do is have a look under the bonnet for anything obvious such as a loose pipe or connector on a sensor. Rather than go to a garage you would be better buying a code reader.

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Your case is similar to mine, it happens early morning and once the car is warm, after restarting the car three times it is gone..

Initially I thought it was the DPF, which I took apart and cleaned, it improved the situation but did not resolve it. Then I thought it was the fuel additive, which was not empty, but I topped up (at a cost).


Initially there was some strange noise that I thought it was the injectors, then after months it sounded like a bad bearing screeching. I changed the timing belt and associated pulleys (fearing a cut and the bigger disaster), to no avail.


I then traced the noise with a flexible pipe and found a leak from the exhaust manifold, used Gun Gum to block it (after cleaning the area) and both the noise and the fault are gone.


I bought the Exhaust manifold gasket (6 Euros) and some extra nuts inn case of damage, and waiting for a nice long weekend to replace it. 


The reason was the DPF reporting wrong pressure to the ECU due to the leakage at the source (Exhaust gasket), so it thinks it is blocked..


The moral of the story, search for a leak before the DPF unit, this may be reporting wrong exhaust pressure readings to the ECU.

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This car is a petrol so no DPF but if there was a leak on the exhaust manifold it could affect the lambda sensor readings. So a leaking manifold could still be the cause of the fault and is worth checking since it does not cost anything apart from time.

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