Try the following:
1. Check that the cable from the Ink Supply Station (ISS) PCA to the Ink Supply Station is correctly connected.
2. Check that the Air Pressurization System Sensor Cable is correctly connected and is NOT damaged.
3. Check all the tubes of the APS and make sure they are NOT pinched or damaged.
4. Faulty APS. Replace the APS.
5. If the error code continues, replace the Main PCA.