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P0420 catalytic converter failure on 1.0 ecoboost 100HP 2014

Mihai Sterpu

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Last year, when I was around ~150.000 Km, my engine problem indicator lighted up for the first time. When I hooked a scan tool, it showed up only the P0420 error code.

The guys from the dealership were a bit unsure at that time so they decided to simply remove the warning and see how it goes from there, hoping it was only a temporary issue.

I only changed the spark plugs (which did have something black and greasy on them) and was advised to use premium fuel (which I already used since I bought the car).

The error code appeared again but I didn't take the car back to the dealership to have a check. Now I'm at 205.000 Km and I'm a bit afraid that maybe other components might get damaged.

Symptoms: none whatsoever, the car accelerates as fast as always, even before the P0420 error.

Last week I took the car to a place where they measure out the emissions and told me they are way over the maximum limit allowed by law.

I would guess that this new information combined with the P0420 error message means my catalytic converter is basically dead?

I would gladly replace it if I knew this problem goes away but I'm afraid something else is wrong with my engine and the new catalytic converter will die as quickly as this one did.

What would you suggest? How would you diagnose this issue?

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different car, I had a Ford Escort. Emissions exceeded legal limit by a long way. I was worried I might need to pay for catalytic converter but it was a faulty oxygen sensor. The oxygen sensor was sending the wrong readings to the ECU which was then fueling the engine wrongly.  To diagnose this the mechanic connected a reader to the OBD socket. With engine running he watched the live readings. he said voltage being sent to the ECU from oxygen sensor seemed too low. From looking at the length of time the fuel injectors were open on each stroke of the engine he said they were opening far too long. He said he thought the ECU was opening the injectors for too long due to low voltage from the oxygen sensor. 

I replaced the oxygen sensor and the car was fine after that. Of course there are other things it could be causing it but I wouldn't leap to replacing the catalytic converter without further checks.

one result of googling that code:



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so youve ignored the code for 55,000 km!! issue was probably the upstream broadband hego sensor, but as it hasnt been rectified the overfueling has now probably damaged the cat also. 

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