TH1, TH2 compare test zero failed. TH3, TH4 compare test failed zero test

Please i need urgent help, all the 3 nikkiso dbb 05 dialysis machine showing this alarm code and wont pass. It says TH1, TH2 compare test zero failed TH3,TH4 compare test zero failed, please any idea on how to resolve these alarms? Thank you for anticipated answers.