New member - Could use some advice

[JayC]

Hi all - My daughter has a 2011 Fiesta that has been causing me nothing but headaches. Im at the end of my rope and Im hoping someone that knows a little more about these cars might be able to help. Im mechanically inclined but unfortunately time deprived.

She has had an ongoing issue of the car constantly throwing a code P0101. Ive replaced the MAF at least 3 times and its been replaced elsewhere by a shop. When it was replaced last time, they told her the intake was cracked and replaced the intake and the MAF.

She also had an issue with the rear O2 throwing a code. I figured it was just a bad O2 and would replace it when I got the chance.

Recently tho, the car has started running rough and she now not only has the P0101 code, she also has:

P0420 - Catalyst Efficiency Below Threshold and
P0606 - ECM/PCM processor

I feel like there is something else up thats causing these codes and I dont really know where to go next. Because of COVID, I havent seen her in about 6 months so Im kind of flying blind her. Im hesitant to send her to a shop because Im afraid theyre just going to charge her some crazy price to do nothing and the car still not be fixed. Thats basically what happened when she had the intake replaced.

Any advice anyone could provide would be appreciated!

Thanks!

 

[scotman]

Where to start? P0606 unlikely that it is a defective pcm. More possible it has a bad ground or some frayed or crushed wires in the harness or connectors.
P0101. Being a 2011 i will assume that there is at least 85,000 miles on it. So, it might be time to get both O2 sensors replaced.
P0420. This one hurts. Especially if you don't have more than that magic mileage i mention above. A catalyst is kind of expensive. But, if the car is in good condition in other respects, it would be worth doing in concert with the new oxygen sensors.
Bad O2 sensors will wreck a catalyst so quickly, and the owners cheapness by refusing to buy a couple of fresh sensors is rewarded with bad fuel economy and deteriorating performance.
Having read your back story on the prior repairs, i have to ask if the "shop" you had do the first repairs was some kind of place that also worked on farm implements or tractors? Maybe best described as "dark, greasy and very primitive"? If it's not like that, then you were ripped off. If it was a primitive shop, they were in over their heads ( and probably ripping you off. Maybe unintentionally)

 

[Handy Andy]

It might help us to see a pic of the engine compartment - especially around the battery.

Why?

Corrosion - a 2011 - they made SEVERAL big changes to the wiring and harness thru the years..

Because of that, we could wind up sending you on a wild goose chase - fruitless and nothing more than a waste of time.

Many of use recognize problems visually, so if a pic or two of good resolution can help us, we can help you diagnose the condition.

Now, I will warn you - and we do understand this...

Not many people like to have their stuff pictured, because of condition or otters coming along with complaints and commentary that isn't helping anyone get this solved. But there are others here that have experience, just not the exact vehicle under their heads, staring at it - looking at it in their garage to help you.

So we know the DTC's, but we don't know the condition of the engine - any help here to help us help you, is appreciated!

 

[scotman]

I understand that Ford had a campaign for the under hood relay and fuse box wiring harness. The 2011 and maybe 12's had corrosion issues in that area.
That problem cropped up about 2014 or so. Also more prevalent in areas where road salts are used.
One way to determine if you have relay-fuse box corrosion is to pull a couple of fuses or relays and look for white deposits. Or take a decent sized screwdriver and tap on the side of said fuse box and see if any white powder falls out of the underside.