HS+LS output EMF capability

Would like to use the HS+LS configuration to control the HV contactors in an Hybrid configuration.  I am reading note about using Diode to protect against EMF.  But I cannot find specification on acceptable EMF level?  Our contactors have built-in EMF clamping diode rated at 150V?
Also how does the open circuit detection in an off state works?  injecting a current i am assuming. How much?  Just want to avoid issue with Dropoff voltage for the coil.