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P0420: Catalyst System Efficiency Below Threshold (Bank 1).

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I've got an error come up.

I had the cat converter replaced after getting the original stolen.

I had a Klarius cat converter and Bosch O2 sensor put on - both from Euro Car parts.

The error has been there maybe 4/5 months now. I just learned to live with it.

Now, I am seeing much lower fuel economy and the engine runs out of Oil and needs to be topped up 3 litres every 2 months.

Elsewhere, I was told I need to identify where the fault is - whether it's the cat converter or the O2 sensor.

HOW to do this... I am confused... I can't find any guides anywhere.

On youtube, I saw 2 videos where people added a '90 Degree Oxygen O2 Sensor Socket' to get rid of the error.

Is this something I should consider?


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How many miles are you doing in 2 months? Your cat could be toast from that amount of Oil consumption.

I think I've seen that error caused by a misfire in other Toyotas - incomplete combustion will throw off emissions too.

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I would be more concerned with the Oil consumption.

If it is burning Oil that badly then the sensors are correct in reporting a fault.

To me it sounds as if either the valve seals or piston rings are badly worn, but you NEED to get this checked out properly.

After the Oil problem is squared away then see if the fault clears.

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