2017 Fiesta ST - 100% stock throwing CEL: P0420

[Ford ST]

The sensor in question that you want to replace is after the downpipe the one farther away from the engine.
The one before the downpipe measures air-fuel ratios the one after the downpipe measures the effectiveness of the converter.


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[PolloVagabundo]

The sensor in question that you want to replace is after the downpipe the one farther away from the engine.
The one before the downpipe measures air-fuel ratios the one after the downpipe measures the effectiveness of the converter.


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even though it said bank 1?

And to replace the second sensor, will it be basically the same method as the one I just replaced or is it reachable from under the car?

sorry - I’m learning as I go, appreciate everyone’s help so far!

 

[Ford ST]

So basically a inline engine like a 4-cylinder only has one bank. A V engine like a v6 would have 2 banks.

May have to go under the car not sure.

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[D1JL]

I will just post my 2¢ worth.
I was a CA Smog Tech for many years and had to do many emission repairs.
I found that it was NOT worth the money savings to use any thing other than OEM O2 sensors.

Here also is the info from the service manual.
I hope it helps.

 

[Intuit]

The sensor in question that you want to replace is after the downpipe the one farther away from the engine.
The one before the downpipe measures air-fuel ratios the one after the downpipe measures the effectiveness of the converter.

Yep. Everyone has been saying the code is reference to the catalytic converter. This means it's either the downstream sensor as Ford ST said, or the catalytic converter itself. (or both)

Hang on to the original sensor you just removed. I'd confirm whether the first/second sensor are the same (think they are) and use it to replace the one that should've been replaced to start with.

If the catalytic converter has failed, consider the possibility that there may be an engine or fuel-additive related reason(s) for it. An engine that's running rich, leaking coolant, running cold, or running leaded fuel, are examples of conditions that murder converters.

 

[PolloVagabundo]

So, We hooked up my friends accessport to check and clear the codes... attached Is what we read.

the code has not came back on since clearing but we will see in the next few days of driving.

 

[PolloVagabundo]

P0420 code is back on!

option one, replace the second sensor next to the downpipe?

option two.. bring the car into the dealer and hope it’s the cat needing replacement?

3yrs old and just under 50k, this makes me sad.

 

[Ford ST]

yeah but the potential of a free OEM converter and those are expensive. Even if you decide to go to a different downpipe at some point you could sell it.
You have so many people buying these cars on the used market now that have mods on them when they would actually prefer to have the car stock.
Just get it fixed it will be well worth it. I know you mentioned about doing some upgrades, so if you do just sell it for a few hundred dollars.

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[Snrub]

I tend to agree, if you've 100% never run a tune, etc., I think it's time to go to the dealer to get your free cat.

 

[jacobc.19]

let me know what happens. I got the same problem

 

[PolloVagabundo]

let me know what happens. I got the same problem

will do!

currently the light will turn off temporarily and then always comes back on.

Have decided we are going to take it in to the dealer, just need to make an appointment when schedules allow us to car pool for the day.

 

[jacobc.19]

will do!

currently the light will turn off temporarily and then always comes back on.

Have decided we are going to take it in to the dealer, just need to make an appointment when schedules allow us to car pool for the day.

I am going next week on the 6th. If I go before you I will lyk lol

 

[PolloVagabundo]

I am going next week on the 6th. If I go before you I will lyk lol

What year is your car? How many miles?
Definitely let us all know, either way.

 

[jacobc.19]

What year is your car? How many miles?
Definitely let us all know, either way.

2019 7000 miles

 

[PolloVagabundo]

2019 7000 miles

how did your appointment go?
What was the verdict?

 

[jacobc.19]

how did your appointment go?
What was the verdict?

they did nothing but send me to tighten my exhaust up and weld it which i did so and i still have the smell. stratified finally sent a tune that took away the check engine. I am going to just leave it for now but i think its the downpipe

 

[Intuit]

............ stratified finally sent a tune that took away the check engine. ...........................

@jacobc.19 - Non-stock programming is not a stock vehicle. @PolloVagabundo has a reportedly 100% stock drivetrain. (which by definition includes programming)

 

[PolloVagabundo]

Did they charge you a diagnostic fee?

they did nothing but send me to tighten my exhaust up and weld it which i did so and i still have the smell. stratified finally sent a tune that took away the check engine. I am going to just leave it for now but i think its the downpipe

 

[TyphoonFiST]

how did your appointment go?
What was the verdict?

What was your verdict?

 

[PolloVagabundo]

What was your verdict?

With the wife not working, the car has been sitting in the garage. Have not scheduled an appointment with the ford dealer yet but hopefully soon. I will definitely post the results in here after they confirm it is the cat or who knows what else.