Main Catalyst Below Threshold...2001 V70 XC

schuyler_mason · Post by **schuyler_mason** » 01 Aug 2010, 12:14

Main Catalyst Below Threshold (Bank 1) is the latest code generated from my CEL. PO442 is the #. Any idea as to what this is pertaining to and is it serious?

Post by **jblackburn** » 01 Aug 2010, 14:00

Clear the code and see if it returns. Most often the problem is just a bad oxygen sensor and not the cat. converter itself.

Post by **JRL** » 01 Aug 2010, 14:09

Not true
It can be a cat converter or an 02 sensor (or both if you're unlucky)!

If you go to Volvo their reader (VIDA) can narrow down what your problem is.
If you clear it, it may stay off for a while but I guarantee you it WILL come back

FCPEURO · Post by **FCPEURO** » 01 Aug 2010, 20:33

I would still clear it and see if it comes back. Also, how is your gas mileage? If it has dropped then I would look at the O2 sensor being the issue more then the cat. If not, then it could be either one.

schuyler_mason · Post by **schuyler_mason** » 02 Aug 2010, 07:36

Let's consider both are bad or going bad, how long can I limp by? Gas mileage is still 24/25-ish.

Post by **jblackburn** » 02 Aug 2010, 07:55

Until your car has to pass inspection again. Until then, it is only mad at the rear O2 sensor/cat. converter, which have nothing to do with the fuel/air mixture, and the car will run fine.

Whack the bottom of the cat. converter and listen for anything that sounds like loose gravel inside. If you don't hear anything like that, and performance on your car is still the same, your converter is probably still OK.

An OBD scan tool will be able to read both O2 sensor readings, at which point you can compare the two values. The front one should osciallate, while the rear one should show a steady .8V.