Hello all,

My 1999 S70 has had an intermittent check engine light problem. An OBDII check revealed a failure in one of the O2 sensor circuits. The problem seems to be related to cold weather. Now that the weather has warmed, the light has not gone on (in over one month). However, I recently failed my state inspection emission testing as a query of the computer reveals several sensor circuits not ready for testing. I understand from the Volvo shop that there is a certain sequence of engine rpm required to reset all of the circuits. Thus far I have driven the car for a month without being able to reset the circuits. The Volvo shop won't tell me outright, but will charge me 1.5 hours of shop time to do it for me. Does anyone know of the correct sequence?