In short, the vent valve system didn’t work, which meant the urea pump had to work doubly hard. Eventually, the pump would fail, resulting in the errors you saw on the dashboard. PSA fixed the issue by using an AdBlue cap fitted with a small pressure release valve. If caught in time, a new cap would fix the issue. If not, a new tank was required.
AdBlue (BlueHDi) An alert is triggered when the reserve level is reached. For more information on the AdBlue range indicators, refer to the corresponding section. To avoid the vehicle being immobilised in accordance with regulations, you must top up the AdBlue tank. For more information on the Supply of AdBlue, refer to the corresponding section.
Since the Adblue system was introduced ~7 years ago there have been, to my knowledge, two recalls, both ~2017. One was to do with the pump wiring harness, and one was to replace the Adblue tank cap. The first was certainly for C4 Picassos, but I don't know whether this affected other Citroens, the cap was on every Adblue fitted Citroen.
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citroen c3 picasso adblue tank capacity
