Hello! Need your advice again: My C4 already had the error message “gas system defective” before the 120Tkm inspection. One of the masters from Dortmund said that the filter and possibly a pressure sensor had to be changed. He sounded quite safe and actually also competent. Well, the car is now a few days back from the inspection. A new filter was installed and also pressure lines changed. The message did not come first. This morning after approx. 5 minutes drive then the well-known experience: Pieppppppp=> Exhaust gas system defective. I don’t think it’s really funny anymore. Since the car was driven about 800km from the inspection I would have guessed that there is a connection between regeneration and message??? Is it then perhaps even so that the filter does not regenerate and thus increases? Who knows more about it? How can one limit the cause otherwise? The guys from Citroen in Do will probably not have a final answer again. And parts we I don’t want to be cuddled, though I don’t want to be unnecessary either. Would be great if you could help. Thanks and greeting Stefan