Issue:

Upon touchdown, CPC automatically activates the outflow valve to reduce the differential pressure, even when both packs are operational. However, if a defective differential pressure sensor is present, it may cause spurious illumination of the CABIN PRESSURE WARNING lights temporarily, despite the absence of residual differential pressure. In such instances, the CAB PR EXCESS RESIDUAL PR alert may not be triggered on ECAM. The CABIN PRESSURE WARNING lights can remain illuminated for up to 30 minutes in such cases.

Solution:

• Flight crew must confirm that there is no residual differential pressure before opening cabin door
• Wait for CABIN PRESSURE WARNING lights to stop flashing or put off Pack 1 and 2 and open one of the cockpit sliding windows. If unable, it means there is some residual pressure and cabin doors must not be opened.
• The flight crew may periodically attempt to open the cockpit sliding window to confirm the absence of residual pressure.

If the flight crew successfully opens one of the cockpit sliding windows, the CABIN PRESSURE WARNING lights can be considered spurious, and the cabin doors can be opened.