I’m coming up with this catalyst fault P0420 and P0430. It’s been on the car since we bought it nearly 12 months ago. It did have a misfire due to some coil packs earthing but these were replaced but didn’t rectify the problem code. Replaced all spark plugs and filters with genuine parts, tried Powermaxx Oxicat cleaner, always ran a minimum of 95 octane but when I can run 98. Have cleared the codes after every time and always come back. I’m leaning towards rear oxygen sensors but don’t want to replace unless know for certain. Drivability or performance hasn’t been affected at all with the codes there. 

I am using a BlueDriver and this is what it is reading on the codes also this on the mode 6. Any one in Oz have a pair of rear sensors from a T6 or 3.2 they can lend for me to try.

The rear sensors are just normal generic bosch 4 wire sensors that have a volvo specific plug on them

https://www.ebay.com.au/itm/O2-sensor-Universal-4-wire-with-instructions-EGO-Oxygen-Lambda-Bosch-EGO-004/153772794280?epid=244957639&hash=item23cd92a1a8:g:udoAAOSw8JxetQ74:sc:AU_RegularParcelWithTrackingAndSignature!2148!AU!-1&frcectupt=true

Otherwise, just probe the existing sensors with the car running

You should be getting sub 100mv, if you see something fluctuating between .1-1v that means the cat is dead, if you see something over 1v it means that the O2 has failed and the heater circuit is flowing electrons into the sensor circuit

    Philia_Bear

    The rear sensors are just normal generic bosch 4 wire sensors that have a volvo specific plug on them

    https://www.ebay.com.au/itm/O2-sensor-Universal-4-wire-with-instructions-EGO-Oxygen-Lambda-Bosch-EGO-004/153772794280?epid=244957639&hash=item23cd92a1a8:g:udoAAOSw8JxetQ74:sc:AU_RegularParcelWithTrackingAndSignature!2148!AU!-1&frcectupt=true

    Otherwise, just probe the existing sensors with the car running

    You should be getting sub 100mv, if you see something fluctuating between .1-1v that means the cat is dead, if you see something over 1v it means that the O2 has failed and the heater circuit is flowing electrons into the sensor circuit

    Thanks, looks to be the cat then, car has only done 130,000k’s so wasn’t expecting/hoping that to be the problem. Fluctuating between .1 to .8v

      Do the graphs for the rear sensors match the graphs for the front sensors?

      You can simply space the rear 02 sensors to stop the ecu coding for cat convertor efficency

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