Try the following:
1. Check all the cables of the APS and make sure they are correctly connected and are NOT damaged.
2. Check all the tubes of the APS and Tubes System and make sure they are correctly connected and are NOT pinched or damaged.
3. Replace ONE Ink Cartridge at a time, checking if the System Error Code disappears.
4. Faulty APS. Replace the complete APS.
Only replace one component at a time and check if the error has gone before replacing another component. Using this procedure you will be able to determine exactly which component failed.