Vehicle is my 2006 Ford E250. Tons of miles (333k) but a new motor about 120k ago.
I'm wondering if anyone has any good results of replacing the downstream 02 sensor to get the P0420 to go away?
Figuring it might be worth it before I have an exhaust shop replace the cat. Or am I wasting my time?
Replacing the downstream O2 sensor will make it more reactive compared to a very used one. So if the catalyst is dead, it will trigger the fault faster.
In theory, you should change the front one for it to have more activity than the rear one.
In terms of the catalyst- have you seen increased oil consumption over time? Unless you have been driving hard, oil/phosphorus poisoning is probably the most likely cause of it becoming less effective.
I think the fact that you got that code indicates the O2 sensor is working. Might be worth looking into whether anything on that bank is affecting the catalyst efficiency or readings, like exhaust leaks, manifold cracks, a fouled plug, excessive oil burning, vacuum leaks or leaky injector. Visual inspection and look at fuel trims. If there is an underlying cause and it isn't corrected, the new cat will eventually suffer the same fate. Of course, it could just be worn out. If the old cats aren't totally disintegrated, you can get a quote from RRcats.com and offset the costs of new ones somewhat.
In reply to alfadriver :
I haven't noticed increased oil consumption. It's always gone through a little oil, but not much (can't remember how much right now). It does produce some grayish smoke out the exhaust in certain situations, like only when the vehicle is warmed up and more often in high load, low rpm situations. And oddly when the front of the vehicle is pointed downhill, like when I back up an incline. It has done it at idle when the front of the vehicle is downhill once or twice. Could that be oil or is it coolant? It's not consistent at all.
Good to know about the front sensor over the downstream one. My understanding what that if the rear one one failing, it could somehow not match the front and think the cat was failing. I guess that's incorrect thinking.
In reply to Tyler H :
It's definitely possible some of those issues are happening. But I am also just wondering if it's the original cat with 333k on it and it's just kaput.
Personally, if that cat isn't clogged and not flowing, I'd probably just use the ol' spark plug non-fouler trick on the downstream o2 and call it good, if it works on catless cars it would definitely clear up the fault on a marginally working cat
Yeah, that thought has crossed my mind. I am planning to bang on the cat today to see if I can hear anything rattling around in there. Any other way to tell if the cat is clogged?
Has anyone tried the cat cleaner products with any success? Or are they snake oil?
In OBD2ville, P0420 is almost always the catalyst. The O2 sensor kinda can't fail in the direction that would trip a code for catalyst efficiency, or if it does, you would likely have an O2 sensor fault code as well.
333k is a long time for a cat. I would just replace it, or you could probably get it to pass emissions with a bung extension (snicker) or an O2 simulator.
Catalyst cleaner might work, but the more likely culprit at 333k is that the platinum has become depleted. It has a fixed life.
Curtis73 (Forum Supporter) said:.... or an O2 simulator.
For this vehicle, I'm not sure an O2 simulator would work very well- the rear sensor is used for many things, and by 2006, the catalyst monitor was more than just comparing the front and rear sensors on a live basis- by then, there was a monitor that looked at the time when the fuel was shut off- noting when the rear sensor goes to ~0 and then seeing how long it took to come back to a normal range. So if the simulator can't follow that general trend, other codes will be set.
(the other thing the rear sensor was used for was very subtle fuel tuning, and without a decent response, that will get really screwed up)
Thanks Curtis, thanks Alfadriver.
I crawled under the van and banged on the cat today (actually there looked to be two of them) and heard nothing noticeable rattling around inside. I guess the platinum is depleted.
I guess it's time for a new cat. Maybe an indie exhaust shop will do it for less than I fear.
Note that ignition problems - and thus raw fuel in the exhaust - can also take out a cat pretty quickly. Early NB Miatas are good at this.
Thanks Keith. I'll keep that in mind. Overall, it has run well. New spark plugs last year. Just the occasional gray smoke as mentioned above.
Funny enough, just yesterday it started occasionally hesitating at low RPM high load situations. I'm wondering if a coil is starting to go. Or the trans. Yikes.
CyberEric said:Funny enough, just yesterday it started occasionally hesitating at low RPM high load situations. I'm wondering if a coil is starting to go. Or the trans. Yikes.
That matched the symptoms I had with my 01 Mustang GT's 2V 4.6 when I had about 300k on it (original motor). I walked out one morning to start troubleshooting the problem coil, and as I was moving the car into the garage, the CEL lit up and told me exactly which coil was the problem. I replaced it with an OEM coil and that solved the issue.
CyberEric said:Thanks Curtis, thanks Alfadriver.
I crawled under the van and banged on the cat today (actually there looked to be two of them) and heard nothing noticeable rattling around inside. I guess the platinum is depleted.
I guess it's time for a new cat. Maybe an indie exhaust shop will do it for less than I fear.
FWIW, the platinum does not disappear (nor the palladium or rhodium, depending on the make up), it sinters into larger blobs that means less surface area for the gasses to contact. That's why recyclers are happy to take your former catalyst- all of the original precious metals are still there.
In reply to dj06482 (Forum Supporter) :
Good to know! Thank you! I hope that's what it is.
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