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