'09 with 5.4, 180k miles. (Please note: I work from home, and don't drive the truck very often nowadays. Maybe a short (< 30 miles trip) once or twice a week if that.)

12/31/22 while on a little get-away weekend the CEL came on. We just happened upon an auto parts shop, so

I stopped in and asked them to check codes. "O2 sensor" code (don't recall the actual code number, but if I recall it said "Bank 1").

Thought to myself, "Ok, take care of this next week." Kept on driving down the road, finishing up our trip and returned home.

Truck was and has been driving fine.

Started up the truck a couple of days later: CEL gone. And had remained out until now (1/16/23).

Went to the local O'Reilly's to have them check codes: P0420 and P0430.

Let me add, the truck has been, for a while now, a strange unpleasant pungent exhaust odor. Not a burning smell (like oil) or like excess fuel, but not a (for lack of a better descriptor) "pleasant" odor. (Yes, I know. I should have addressed this already. I own that.)

So, wondering if this all ties together: O2 code, exhaust smell, and simultaneous P0420 & P0430 codes? But also, to me, what's odd is having both cat codes fire off at once.

Any thoughts, suggestions?

Thanks y'all

Can't bad cats give off a rotten egg smell? I wonder if there's another condition such as running rich for a long time that may have caused them to fail. It's a 14 year old truck so wouldn't be shocked if they're bad.

Eta the smell could be coincidental. My wife's older car has an unpleasant odor from the ac at startup, then it subsides.

How's your coolant situation? Are you missing any coolant?

Also how long have you been sitting on that tank of gas?

You could start with o2 sensors, then move on to cats if that doesn't solve it- but at that mileage if it were me I'd get some ebay cats and new o2 sensors and call it a day

A good scan tool with live data can get temp data off your cats and also show if your o2 sensors are cycling normally within range from upstream to downstream. If something has fouled the cats and they're burning a lot of unburied fuel you might be running rich due to a bad injector or a bad feedback from a sensor, or some other cause for rich condition. Extra gas vapors getting past combustion can cause cats to get sooty and run hotter than normal or make odors.

Wife's QX56 has these codes that popped almost simultaneously a few years ago and I've changed plugs, injector cleaner, air filter, clean MAF sensor, but the CEL still comes on about half the time. I just get it inspected when it's off.

Try an italian tuneup, as MBL said.

Tend to agree with MouthBQ's line of thinking.

Thinking about it, I guess another way to describe the exhaust smell would be a "heavy exhaust". I dunno, can't quite put my finger on it. But I don't think of rotten eggs when smelling it.

So maybe it's running rich and I'm smelling carbon. Maybe a vacuum leak?

Or I may need to check the fuel system (spray carb cleaner around the intake manifold gaskets, look for the idle to kick up).

Or maybe an exhaust leak or failing egr...

I'm kinda leaning this way due to the fact both codes (representing both banks and/or Cats) fired off at the same time. Would seem against the odds for both cats to fail at the same time, so something upstream of them?

Any more thoughts on this anyone?

And yes, while I'm at it, with the miles on this truck, may just change all 4 O2s and both cats while I'm at it.



To help fund all this fun, anyone want to buy a complete 475+HP SBC 350, ~600 laps (most on 3/8 track, so that's only about 255 miles...)?

I would clear the codes and run a tank or two of gas through with the additive Techron or Seafoam. It could be months before the light comes back on.

Generally driving with the check engine light on will not hurt your engine. If it starts flashing, then you have a serious problem.

Based on what you have told us so far, it sounds like your catalytic converter may need to be cleaned or replaced.

How old are the plugs?

Buy a bottle of BG 44K and give it a try

I've ordered both a bottle of Techron and Cataclean. Figured I would give them a shot.

As soon as the weather clears I'm going to start checking for any exhaust or vacuum leaks.

1agswitchin4lanes said:

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How old are the plugs?

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Just changed them and coil boots <500 miles ago

RC_57 said:

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1agswitchin4lanes said:

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How old are the plugs?

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Just changed them and coil boots <500 miles ago

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Motorcraft?

1agswitchin4lanes said:

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RC_57 said:

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1agswitchin4lanes said:

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How old are the plugs?

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Just changed them and coil boots <500 miles ago

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Motorcraft?

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Yes, SP509Xs

NGK 58975 boots

Bumping this so it's on my watch list.

Mine popped a P0430 today.

2018 2.7L with 111k; Motorcraft plugs replaced last month; white...

No noticeable symptoms that I can tell (sluggish, bad odor, etc.). Runs fine though I did notice a slight drop in my (computer calculated) MPGs on the last couple of tanks of fuel.

RC_57 said:

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1agswitchin4lanes said:

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RC_57 said:

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1agswitchin4lanes said:

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How old are the plugs?

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Just changed them and coil boots <500 miles ago

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Motorcraft?

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Yes, SP509Xs

NGK 58975 boots

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Clean mass air flow sensor with MAF cleaner, clean throttle body. Can of BG44K in the fuel tank. Disconnect negative terminal for 20 min.

dodger02 said:

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Bumping this so it's on my watch list.

Mine popped a P0430 today.

2018 2.7L with 111k; Motorcraft plugs replaced last month; white...

No noticeable symptoms that I can tell (sluggish, bad odor, etc.). Runs fine though I did notice a slight drop in my (computer calculated) MPGs on the last couple of tanks of fuel.

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Bg44K, clean TB, disconnect negative terminal.

If this doesn't help, just get an aftermarket tune that turns the rear 02 sensors off.

1agswitchin4lanes said:

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RC_57 said:

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1agswitchin4lanes said:

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RC_57 said:

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1agswitchin4lanes said:

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How old are the plugs?

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Just changed them and coil boots <500 miles ago

---

Motorcraft?

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Yes, SP509Xs

NGK 58975 boots

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Clean mass air flow sensor with MAF cleaner, clean throttle body. Can of BG44K in the fuel tank. Disconnect negative terminal for 20 min.

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Thanks 1ags. I'll give it a try.

Nothing ventured but a few $s and my time.

I bought some BG44K last night and I'm picking up some throttle body and MAF cleaner this afternoon. Guess I'll blast everything this weekend.

But my light did turn off this morning. It was on at 6am when I took my daughter to basketball practice...but didn't come back on an hour later when I left the house for work. I got gas on the way home last night, FWIW.

Burning bad fuel maybe playing games with my O2 sensors?

Will turning off the rear O2 sensors have a negative downstream effect in the future? I read something about that not being a very good/wise long-term solution.

Bumping this because I have a P0430 in my 15 F150 3.5 L Ecoboost and I'm due for inspection. Bg44k and cleaning sensors worth it?

For what it's worth, shortly after receiving 1ags advice, I used the suggested BG44K (I didn't clean the TB. Was going to do that another day).

The CEL disappeared and had not reappeared up through earlier this week when I sold the truck.

So it (the 44) paid off for me.

RC_57 said:

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For what it's worth, shortly after receiving 1ags advice, I used the suggested BG44K (I didn't clean the TB. Was going to do that another day).

The CEL disappeared and had not reappeared up through earlier this week when I sold the truck.

So it (the 44) paid off for me.

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Magic in a bottle.

Good update!

Good bump. I also had an issue. I ran BG44 through. It cleared the codes for a week or so and then they popped again. I ended up replacing the O2 sensor on the driver side cat (downstream). Light has been off ever since.

It was a pretty simple job once I figured out how to disconnect the cables. They're kind of tough to reach upon initial inspection.

dodger02 said:

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Good bump. I also had an issue. I ran BG44 through. It cleared the codes for a week or so and then they popped again. I ended up replacing the O2 sensor on the driver side cat (downstream). Light has been off ever since.

It was a pretty simple job once I figured out how to disconnect the cables. They're kind of tough to reach upon initial inspection.

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Any special tools necessary? I am mostly concerned with getting my inspection done in the near term, so a week of no CEL would be good, but I anticipate needing to do O2 sensors eventually.

GarlandAg2012 said:

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dodger02 said:

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Good bump. I also had an issue. I ran BG44 through. It cleared the codes for a week or so and then they popped again. I ended up replacing the O2 sensor on the driver side cat (downstream). Light has been off ever since.

It was a pretty simple job once I figured out how to disconnect the cables. They're kind of tough to reach upon initial inspection.

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Any special tools necessary? I am mostly concerned with getting my inspection done in the near term, so a week of no CEL would be good, but I anticipate needing to do O2 sensors eventually.

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Would suggest soaking where the sensor meets the exhaust with penetrating oil for a bit. Let it sit and do it's work

Then use flare nut wrenches.

Worked for me in the past when changing sensors on an F150

Just a wrench. I did use some break-free just in case the sensor was seized up. It took some muscle and I had to use a short extension to get more leverage.

RC_57 said:

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GarlandAg2012 said:

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dodger02 said:

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Good bump. I also had an issue. I ran BG44 through. It cleared the codes for a week or so and then they popped again. I ended up replacing the O2 sensor on the driver side cat (downstream). Light has been off ever since.

It was a pretty simple job once I figured out how to disconnect the cables. They're kind of tough to reach upon initial inspection.

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Any special tools necessary? I am mostly concerned with getting my inspection done in the near term, so a week of no CEL would be good, but I anticipate needing to do O2 sensors eventually.

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Would suggest soaking where the sensor meets the exhaust with penetrating oil for a bit. Let it sit and do it's work

Then use flare nut wrenches.

Worked for me in the past when changing sensors on an F150

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Thanks for the tips!

Another bump on this one! 2018 3.5 ecoboost, 120k miles with P0420 and P0430 codes that started around 10k miles ago and keep coming back every couple hundred miles. No rotten odor. I've replaced all four O2 sensors and ran a can of 44k. That helped duration between CELs but wont kill it.

Plugs were changed at 70k miles. I guess TB and MAF cleaning is in my future. Any other suggestions appreciated!

Just FYI: if you're not in an emissions county, you can probably ignore them. My expy has been popping those codes for almost 100,000 miles.