Hi guys driving my car and eml came on and now got diagnostic machine on and it come up with po420 catalyst below threshold, on checking live data the MV of the sensor bank 1 sensor 1 is reading between -0.102 and 1.275 thought this might be a bit strange for it being so fat apart any help would be much appreciated.

What engine?

Hi alexp999 the engine is the 1.0 3 cylinder ecoboost.cheers

As a first off I would simply clear the fault code then see if it comes back.

Had the same code recently, deleted it and it hasn't returned. Have done over 150 miles since, urban and motorway.

Hi thanks for your reply I've deleted it twice and has come up the same code again.

My next approach would be to replace the upstream sensor. As far as I'm aware, the readings you quote are outside the normal working range of a good one (around 0.1 to 1.0).

Upstream sensor is a wide band sensor so shouldn't fluctuate like a narrow band sensor would normally do. Wide band sensors are not to easy to diagnose. 

Thanks for your reply here is a screen shot of onboard diagnostics

23 hours ago, Coreysdad2011 said:

Hi guys driving my car and eml came on and now got diagnostic machine on and it come up with po420 catalyst below threshold, on checking live data the MV of the sensor bank 1 sensor 1 is reading between -0.102 and 1.275 thought this might be a bit strange for it being so fat apart any help would be much appreciated.

By the looks of the diagnostics screenshot you mixing up the figures from sensor 1 and sensor 2

Sorry but what does that mean would u replace the foremost sensor?

By the looks of your Data there is nothing wrong with either O2 Sensor. If there was a fault with them then I would expect an O2 specific fault code.

The Cat Temperature is a little bit lower than I would have expected. That may be because the car was not warm enough yet or because the Cat is past its best.

I had a code of p0420, which was catalyst below threshold

I had a code of p0420, which was catalyst below threshold u think it should be replaced.

I have the exact same problem - 2016 1,0 Ecoboost 91000 km. It is difficult to diagnose this code as there are many components that may play a role. Ford just advised me to replace the cat. One of the independent mechanics I refer to told me that the cat is in fact 95% efficient but the engine software is just set at very low tolerances and here is the result. What I have done: clear the code, change the gas station, regular use of Liqui Moly cat cleaner petrol additive /may help for 3000 - 5000 km / but still have the check engine light on regularly. In my case the check engine light always pops up at high speed on the motorway! Yesterday I changed my 4 year old spark plugs /52 000 km/. We'll see ...

20 hours ago, Coreysdad2011 said:

I had a code of p0420, which was catalyst below threshold u think it should be replaced.

Ultimately it's your decision.  But we've seen quite a few of these now.  The only long term fix seems to be replacing the cat.  Other solutions may appear to work for the first few months.

3 hours ago, Tony Roman said:

Ford just advised me to replace the cat.

Possibly you just misheard ?

Ford just advised me to replace the car !