Ford Focus Coupe-Cabriolet - Ford Focus 2009 1.6l (Manual) - P0420 Live Data Re

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Mon 28 Apr 2025 18:57
Ford Focus Coupe-Cabriolet - Ford Focus 2009 1.6l (Manual) - P0420 Live Data Re - EastLondonLiving

Hi all,

I've looked at some live readings on ForScan to assess a P0420 code that popped up. To my untrained eye, everything looks fine, bar the 02 Bank1 Sensor 2 giving near on identical reading to 02 Bank1 Sensor 1. While they are neither 02 are switching between rich and lean as quickly as I like, I don't know if I'm expecting too much here from my 2009 Focus engine.

The MAF sensor is rising with the revs, as I believe to be expected.

The MAP sensor decreases with rpm, as I believe to be expected.

Fuel trim looks fine, rises with revs with the top end around 10%, as I believe is normal.

Braking results in both sensors to switch to lean, as I believe is normal.

I'm simply trying to exclude any other possibilities before I start looking at a new cat. Any nudges in the possible right direction would be a big help. Does anything look out of the ordinary from the data?

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Mon 28 Apr 2025 20:13
Ford Focus Coupe-Cabriolet - Ford Focus 2009 1.6l (Manual) - P0420 Live Data Re - elekie&a/c doctor
That code is flagging a common problem with catalytic converter efficiency. You’ll find the emissions are likely to be within spec for the mot test . Cheap solution is to put a spacer on the rear lambda sensor which fools the ecu into thinking the cat is ok . About £15 or less
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Tue 29 Apr 2025 12:19
Ford Focus Coupe-Cabriolet - Ford Focus 2009 1.6l (Manual) - P0420 Live Data Re - Gibbo_Wirral

If you need a new cat, I've found CATS2U to be decent for aftermarket ones

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