Hi everyone,

I have a CEL code P0420, related to the catalytic converter. My 2013 Volvo S60 T5 AWD has about 146,000 miles on it and drives beautifully.

After some research related to this code I’d like to check and likely replace the oxygen sensors, but can’t seem to find where they are located (front and rear).

Any direction on where to find them is greatly appreciated.

Does anyone have experience swapping these out? What is the typical process / tools needed or recommended?

Thank you

 

you'd need to go under the car and follow the exhaust from the turbo through the down pipe and then through the catalytic converter. The O2 sensors are the wired devices that screw into exhaust. The upstream front sensor is closest to the engine, the downstream rear sensor is the one after the catalytic converter. Typical process is to lift the car then determine how best to access the sensor (varies by model). you'd disconnect the sensor at its connector (by the firewall) and use an O2 sensor socket or similar tool that allows the wrench to install with the wires in place and simply undo/ redo. With that said, replacing the rear O2 sensor may not fix your code. The code is saying the rear sensor is still detecting oxygen after the converter, meaning the NOs and HCs have not been fully converted. Its possibly the sensor is bad but more likely its saying the converter is not up to snuff. One work around popular on older cars is to insert a cel-boss spacer to take the sensor out of the air flow but at the end of the day, your converter may not be doing its job. So you can try dropping in a $150 sensor but don't be surprised if you still have an issue with the cat.

 

I had a similar issue with an old Subaru, and what mt6127 says is dead on correct. My problem was a "faulty cat" which really could just mean an aftermarket, not-quite-the-correct-model cat, so no matter how much I reset that P0420, it eventually kept coming back. It has to do with the duty cycle of the engine as to how soon it comes back on. Sometimes I could go a couple weeks, sometimes it would come back right away, the next time I started the car. Unfortunately a new sensor will likely not fix your issue, so it's either live with the code (which I did), take the sensor out of the flow like mt6127 mentioned, or bite the bullet and replace the cat. If your state or region requires emissions testing, it limits your options.

 

As other have said - your po420 code does not mean your O2 sensors are bad, actually it probably means they are working correctly and finding too much oxygen in the exhaust stream after the converter. Replacing the sensors will just deplete your cash source to be able to fix the real problem. ( put an extender on the rear sensor and see what happens might be the cheapest test - of course I am not advocating modifying an emission device - just suggesting a possible test.)

Quote from somewhere on the internet -

"Can a bad O2 sensor cause a P0420 code?
The cause of this trouble code is most often the catalytic converter – which may get damaged by other problems with your car's engine like misfires. Bad O2 Sensors can cause the this trouble code, but is pretty rare".