{HEAD ~ Such a condition} may be requested by {TAIL ~ the routine} based on an evaluation of emission control device performance, and based on a fixed number or time of engine and vehicle operation 
requested by
{ HEAD ~ Such a condition } may be requested by { TAIL ~ the routine } based on an evaluation of emission control device performance , and based on a fixed number or time of engine and vehicle operation
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH