Q: 2006 Volvo S40 - Engine cut out twice last week - This week check engine light w/ P0420 code reading.

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Two weeks ago I got a check engine light that keeps turning on and then turning off. Last week, my car cut off twice in two days when I was first parked, then backed up, then turned off when I went to drive forward. It was shaky both times immediately preceding cutting off. When it turns off all lights on the dashboard light up. My friend read my CEL today as it turned on again for a read and it says P0420 and P0420 FD.

My car has 160000 miles.
My car has an automatic transmission.

Hi there. When the oxygen sensors have readings that are similar to each other, it is an indication that the catalytic converter is not working as intended. If the voltage of the downstream oxygen sensor decreases, and begins to fluctuate like the upstream oxygen sensor, it means that the oxygen levels are too high and the Powertrain Control Module (PCM) will store the P0420 trouble code. This is typically caused by one or both O2 sensors being damaged or the electrical harness that connects to the sensors is faulty. It would be a good idea to have a professional mechanic come to your location to complete an inspection, so they can pinpoint the exact source of this issue and determine what part repairs are needed to resolve this issue.

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