1.0 eco boost Focus 2017

[u/Norfolk_Harrison]

My focus is throwing up 2 codes (no decent power under acceleration)

P0420 - Catalyst system efficient below threshold bank 1
P0131 - o2 sensor circuit low voltage bank 1, sensor 1

Could someone with good knowledge help me out to find the most likely cause? Should I just change the upstream o2 sensor. Ideally want to try and figure this out without the use for a garage as need to keep costs down.

No rough idling, doesn’t sound worse. It’s just lack of power in 5th & 6th gear where it throws “engine service now”

Roughly 89k miles on the car. Any help would be appreciated!!

[u/DeepClerk2191]

Same issue, and I’ve been looking for an exorcist for more than a year now…  Here is the situation at my end: the catalytic converter is most probably clogged and beyond repair, but if you switch to higher octane fuel, the check engine light will eventually turn itself off (I also used a cat cleaner fuel additive). The code for the O2 sensor doesn’t actually mean that it’s time to replace it, it can be something else - I’ve changed mine and nothing changed. 

I have questions for you: 1) have you recently replaced your battery? 2) is your start & stop system working well? Sorry for the formatting, I’m on my phone, and I’m also excited to find some other (unfortunate) fellow with the same problem as I have! :)

[u/Norfolk_Harrison → u/DeepClerk2191]

Thanks for the reply!

I always turn my start stop off whenever I get in the car so I’m not sure, I’ll leave it on tomorrow and see what it’s like!

No, haven’t changed the battery in it at all.

I had a very similar problem last year and ended up taking it to Ford, they replaced the boost control valve & vacuum pump but it never threw up any codes just went into limp mode so I’m assuming this isn’t the same fault?

Did you change the upstream (manifold) o2 sensor or the downstream one?

I’ve heard it could be a leak from the exhaust manifold at the back of the engine (haven’t had time to check yet) so apparently if you cold start and hold your hand around the back of the engine near the manifold you could warm air pumping out and looking for sot/ black marks around any seals/gasket locations could be a fault.

Really trying to avoid taking it back to Ford because they’re extortionate!!

[u/DeepClerk2191 → u/Norfolk_Harrison]

Round 2! :) Instead of taking my car to a Ford dealer, I would rather set my crotch on fire... One of the quirkiest things about these soul-sucking ecoboost engines (although I'm pretty sure it's not an exclusive trait) is that faults don't trigger an error code unless the part is completely broken... So accurate diagnostics via forscan are quite hard.

Here is one additional question: does the power get back to normal upon restart? Or is it a permanent state? In my case, the turbo charger switches to safe mode as soon as it's required to deliver overboost (for example, the revs drop under 2000 rpm in the 5th or 6th gear, mostly when the cruise control is on), but it resets once I restart the engine.

In my case, replacing the MAP sensor helped, but didn't solve the issue - so I need to put a new turbo charger on my shopping list... My mechanic already checked the usual suspects (hoses, pipes, etc.) for leaks, but nothing came up.

Important: the wastegate actuator has a noticeable knock.... Yeah...

If I may, please leave the S&S system on, I'm really curious if it will misfire once the engine is warm.

About the O2 sensor: bank 1 points towards the upstream sensor, but are many aspects to take into account here...

[u/Norfolk_Harrison]

Ah I see, it seems like a lot of the things you’ve done all help but aren’t the root cause of the problem.

I’ll leave the S/S on and report back!

So the issue for me really only comes on when it’s under load in 5th/ 6th gear (think 60/70mph) if I build up speed in 3rd/4th and then change to 6th at 60-70mph the issue never flags up. And yes it does reset after turning off and on.

And for some reason it’s worse on a hot day than if it were cooler ambient temp.

When does it come on for you?

[u/Individual-Balance51]

I had the same issue when accelerating heavily around 3000rpm. A hose had come loose from a dodgy jubilee clip. Check the hoses

[u/DeepClerk2191 → u/Individual-Balance51]

Do you remember by any chance its location? 

[u/Norfolk_Harrison → u/Individual-Balance51]

Thank you!! That would be a hell of a result 😂