Volvo: odm codes, o2 sensors, volvo s70

Question
check engine lite on 1999 volvo s70. One shop says o2 sensors before and after cat. converter. Next says there are no fault codes found. Why the discrepancy?? Also boots gone on axles -guess they are right as car is a 1999.

Answer
Kathy Rich,
I always replace the entire axle when the boot tear. Axles are about $140.00 each. Maybe the first time the codes were read they were also cleared. Is the check engine light on? If you doo have HO2S codes always replace both sensors and use factory new ones. Ask if the one you are getting are the latest updated version.