Blue Adblue cap, should be ventilated, but is not? Could someone test their cap?

[bjornove]

Berlingo 1.6 HDI 2016. Changed Adblue tank after 105 000 km. Had to pay because just out of warranty. After change of Nox sensor at 120 000 km I have had 4 emission fault with count downs (now at 142 000 km)  My mechanics could not find any fault so just reset ECU.
 
When the last one happened (before count down happened) I had a crazy idea:
 
I disconnected the battery and removed the Adblue cap. Reconnected battery and started the engine. Result: warning was gone. I was thinking: could my problems be with the Adblue cap. The cap is the blue one with white center. So should be ventilated. Could there be a fault with the cap?
 
Cleaned the cap in water and tried to suck out air from inside to see if it really was ventilated. Result: could not suck in any air no matter how hard I tried. Could this be the problem? A faulty cap which does not let in any air? I did not put in the cap again and drove the rest 300 km or so without the cap, just covered the Adblue filling hole with a piece of cloth. The emission fault did not come up again.
 
Disconnect and reconnect the battery has never worked before to remove the error, so could the problem be the cap not letting in any air?
 

[Sol]

The white center is the ventilated one. Why not just drill a tiny hole in the cap you have. 1 or 2 mm drill will be fine. By the time the error appears due to the cap recall not being fitted, it is because the tank has collapsed and crushed the pump.

I don't think you have this problem but you never know.

Also if you don't do a lot of miles, and the Adblue in the tank is more than 1 year old, it can crystalize in the tank and injector, causing an error due to high NOx readings at the CAT.