new to this forum but i have been over at volvoxc.com for a while now. i have a '00 v70xc with about 85k miles. recently been getting some trouble codes and wondering if they might be related. little more history, the operating temp seems to be running low. i think i have a faulty stat so that will soon be replaced.

first code is p0128 (coolant temperature Below thermostat regulating temperature) which i think is due to the faulty stat. the second is p0422 (main catalyst below threshold bank 1). i got to thinking this moring that maybe the p0128 (faulty stat) is causing p0422 since the engine does not stay at the proper operating temp.

any thoughts?

thanks.

 

If the coolant temp sensor or thermostat is bad it will make the car run Rich.
Which will set the Cat code.

 

thanks for the reply, it makes sense.

do you think i can get a new thermostat at kragen or autozone or do i need to find an import auto parts store?

 

You should be able to get one from anywhere.

 

installing the new stat tomorrow. i will give an update.

 

got the new stat installed. haven't tested it yet but i tested the old stat. drop it in a boiling pot, open right up. it has now been sitting for about an hour in 40 degree air and is not completely closed. i tend to think this was the root of my problem. i cleared the codes and we will see what happens.