Hello,

I have a 2002 S40 with 136k miles. Yesterday check engine light came on. Pulled the codes and came up with P0420 01/02 and the second one P0420 02/02 Pd.
I did a quick search and found this could be the oxygen sensors or the coolant temperature sensor. Does this sound right? Anybody has had this problem before? Is it easy to change the sensors myself?
Thank you so much for the help !

 

From what I've read it's the top (aka front) O2 sensor. When I replaced mine I used the generic Bosch unit from Advance Auto Parts, Part No. 15733. It was not hard at all to splice into the Volvo's wiring harness. IPD sells a plug and play one for a little more:
http://www.ipdusa.com/Volvo-S40V40-2...-423-425-5203/

Do you have the conversion wiring harness for the O2 sensor on the 2002 model? On the 2001 there was a recall to fix a mixed up O2 wiring harness. 2 of the 4 wires were reversed from the factory. A simple harness was installed to swap the wires to where they should be for the heated O2 sensor.