Hi All,

Not been posting for a while but I have stuck my head in now and again, simply because I've had no real problems with my S-Type.........until now!
Coming home from mothers yesterday, Christmas day, check engine light comes on. WTF????
Plugged it in with IDS, got the code P0430, bank 2 cat problem.
That was the only code given.

So I've gone out this morning, checked for air leaks round the engine, sprayed everywhere, nothing found.
I've still to check the LTFT and STFT, and I'll see if I can remember how to check the O2 sensors before I decide if/when to replace them.
I shall also swap them around to see if any code follows them

My question is, if I have to replace the catalytic converters, I'm thinking of the MagnaFlow ones. But what is better in regards to cell counts?
I have seen 200, 300 and 400 cells but I have no idea as to what the difference is. I know it is connected with flow but that's about it.

For our american cousins, I'm based in the UK.

Thanks in advance for your opinions

 

Don’t start thinking about changing the catalytic converter’s yet. When I had that code it was a air leak. But very small but apparently enough to make it look like the cat wasn’t working well. But since I had brand new catalytic converter’s on it I knew it wasn’t the catalytic converter’s so I kept looking. And using spray to try to find the vacuum leak will not help. The PCM adjust to quickly to resolve the change in mixture as it picks up the spray so you will not hear much happening with the motor. You need to monitor the O2 sensor outputs and the short term fuel trims to look for a change when you do the spray

Here are the signals you should monitor.


Signals from top to bottom
O2 sensor one bank one current
O2 sensor one bank two current
O2 sensor two bank one volts
O2 sensor two bank two volts

O2 sensor two bank one
O2 sensor to bank two
STFT Bank one
STFT bank two

 

+1 on that!

In my overinflated opinion, if you don't find any vacuum leaks (as detailed above), I'd suggest replacing the upstream O2 sensor on that side for a cat efficiency fault (P0420 or P0430).

These codes, referring to catalyst efficiency, are determined by sampling "dirty" exhaust entering the cat, as measured upstream. The sensor sends out a reading and the PCM instantly adjusts the air/fuel ratio to compensate, constantly switching back and forth. The switching rate upstream (fast switching is basically good) is then compared to the switching rate downstream of the cat, where the switching rate should be slower to indicate the cat is cleaning the exhaust as designed. Since sensor switching tends to slow as they age, I tried a new upstream sensor on my '02 to increase the difference. I kept the old sensor downstream, as slower switching there is good, as far as the cat efficiency monitoring is concerned.

This took care of a marginal cat on my '02. Please note this is only applicable for a cat just slightly over the edge. It won't help with one that is severely damaged. 2003+ models use a different (read: more expensive) type of upstream O2 sensor, so it may not be worth the gamble. But on an earlier model, I think it's worth it. Call me Mr. Vegas...

 

Well, my original question was.........IF..............I have to replace the cats.................

I haven't ruled out the o2 sensors yet as I haven't got round to checking them.
As I also said, I'm going to switch them to see if the fault follows first; if it does I know it's the o2 sensor, if it doesn't I shall continue........

 

if you can get a few pics of the signals like I posted FIRST, it gives us a baseline to see what your change does to it. Watch the signal for a good 1/2 hour or more to see what they do as the pcm makes adjustments

and after you change it, watch the signals again for a good long time as you might initially see some outrageous outputs but keep watching and see what they do. If you quit early you might be fooled bc the the pcm is making its changes

 

(note the wink emoji, meaning this was all meant in good fun and you don't really have to report me to the moderators...)

 

Depends what you mean by better. The more cells per CI, the better your cats are at reducing emissions. The lower the number, the less efficient they are, but the greater the flow (& noise) & vice versa.

 

Right now you have malfunction indicator light for cat efficiency. And I’m assuming you don’t like it. Well if you were to change to a different catalytic converter that has better flow it will have less catalytic plates inside it and will be less efficient and could possibly throw a code for cat efficiency

 

The OP only asked what the differences are between cats if he has to change them. It's a valid, stand-alone question. He's not suggested he's going to fit higher flowing cats.

 

oh ok. They are different in the catalyst material is less densely packed and freer flowing in the lower number cats.

 

I had a problem with passenger side Cat due to a wiring problem that kept causing the dumping of un-burned fuel from the # 3&5 (#2 & 3 in a 2002). Completely destroyed it and turned to insides to a form of sandy dust. I replaced both with Magna-flows some 6.5 years ago and have never had a problem since (also had to get the trigger wire fixed that caused the problem in the first place).Changed all 4 O2 sensors at the same time and considered it a maintenance issue.
If the Cat is going bad, you will start getting internal detonations which which be obvious especially under stress (such as higher acceleration going up a hill). If you are in a garage you will have lots of bad smells of carbon, gas and sulfur that will be obvious. Also check the airflow on the bad one vs. the good one.

I would want to know where your fuel trims are to solve the potential problem that created the issue, although it is possible for them to fail on their own.

Tom in Dallas/Plano
2005 S-Type 3.0 117k

 

Also do you ever remember seeing a flashing CEL?

Tom