I had the engine light come on this last Saturday morning. Took it to the auto store to run the code. Didn't catch the code number, but the guy showed me where it said cats weren't getting sufficient airflow. He told me they needed changing. Problem is, I just changed them out last year. So now I'm thinking I might have to change the O2 sensors. It's an 07 5.4 with almost 376k miles on it. Still runs and looks great. Last year the code read for an O2 sensor, but another guy told me it was definitely the cats.
So, is this what you all are thinking also? That the O2 sensors need replacing? I did clean my MAF sensor out as it may have been a while since I did that. Plugs and coils are only a couple years old.
Another question on the O2 sensors, I see places sell them as upstream and downstream, yet others sell both upstream and downstream. Are these all identical, or is there 2 different types for the upstream / downstream?

 

Did he reset the code after reading it and did it go away or is it still there?

You need to tell us the actual code because there are a plethora of codes that relate to the O2 sensors and without it we don't know if it's the upstream or downstream that's having issues or what the issue might be.

The upstream sensors are used by the pcm to control the air fuel ratio.
the down stream ones are only used by the emissions monitor part of the system to check the catalyst efficiency
The sensors themselves may well be the same upstream and down I'm not sure on that

 

I'll have to find a reader and catch the exact numbers for the code.

 

I'm going to assume a 420 code and if aftermarket cats, I've found their life expectancy is short.
Might want to try something like this, at least to get rid of the light:
https://www.shopgoodyy.com/products/...iABEgJRQfD_BwE

https://www.shopgoodyy.com/products/...yABEgK3u_D_BwE

 

they are cheap for a basic one. A must have if your want to do any DIY repair/diag. Not worth it to otherwise have to run to a shop or parts store every time just to read/clear basic codes.

 

What is it you say the life expectancy is short on? The CATs or the O2 Sensors?

 

Generally, aftermarket cats don’t have the same amount of materials in them that OEM cats do.

As far as O2 sensors, you’d be next in line as far as posters replacing parts that work because they didn’t troubleshoot a code properly.

 

Oxygen Sensors for my 2007 F-150 4.6L STX are two different part numbers and the 02 sensor's connector color matches the wiring harness connector color.

O2 sensors, As-Found 3/25/2020 is as follows

UPSTREAM (DY835) Grey Connector

XL3Z-9F472-AA (As-Read for the one with Grey Connector and located upstream, both banks)

XL3Z-9F472-AA (Ford Parts Desk based on last eight digits of VIN 1 of 2) $88.18

Is the Ford XL3Z-9F472-AA Sensor exactly the same as the Motorcraft DY-835? YES!

200404 Purchased (Amazon) new XL3Z-9F472-AA {DY-835} and 4L3Z-9G444-AA {DY-992} to be installed on Bank 2, passenger side.

DOWNSTREAM (DY992) Violet Connector

4L3A-9G444-AA (As-Read for the one with Violet Connector and located downstream, both banks)

4L3Z-9G444-AA (Ford Parts Desk based on last eight digits of VIN 1 of 2) $83.98

Excellent O2 Sensor info at:

http://www.walkerproducts.com/_fb/faq-technical.html

 

Cats

 

Thank you all for the info. I ran the code and it came up with p0430. Since the Cats were just changed out last year, I'll probably replace both downstream sensors and put extenders on them. I cleared the code to shut the engine light off. We just got back from camping this last weekend. The truck still got 16 miles to the gallon on the highway.