Good Morning fellows, and fellow-ets...

My CEL is on. I've cleared it and it can take a while, but it returns. Code is p0420. "Catalytic System Efficiency Below Threshold " Bank 1.

So, when I read about TRIMS I am sure that the Google results aren't providing info for a 20+ y/o car. But they say, and the only other thing I have to compare these numbers to is my 2004 XKR with modified CATs, is that the LTFT are supposed to be stable-ish. Trims are much more stable on the XKR. The 2002, in and over very short distances, do fluctuate. Dramatically?. Strange things is both A and B generally match, as high as +13% or so,,, but say taking off from a light, I see numbers quickly go as low as 3 or even 0%... Never goes negative... What is that? They BOTH do this and match down the line, for the most part.

I've tried (don't laugh) Cat-Ah-Clean. Didn't help.

If replacement is the direction I have to go and there is nooooo choice, what are the options for NEW and replacement CATs? What have y'all done?

I've seen aftermarket CATs and am wondering if anyone is aware of a good maker?

What do you all think I should try or be getting ready for?

Thanks MUCH for your help and offering your experience.
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The fuel trim regulates according to signal from your upstream oxygen sensor.
The downstream oxygen sensor detects if your catalytic converter functions properly.
So your problem may be the catalytic converter, or the downstream oxygen sensor.
If you switch the connectors for the downstream oxygen sensors (bank1 to bank 2 and vise versa) and see if you still get the code for bank 1, then you will know where the problem is.

 

THIS is why come here...
I will give it a try...

 

Good Morning Good Folks.

So, I haven't taken any steps just yet OR haven't taken that perfect first step advice of swapping the sensor plugs and seeing what happens.

Being a man of modest means (with a broken washing machine that needs replacement, lol) I've been looking around and planning for what might be coming down the road, stashing ME pennies...

Although it's a 40k motor, mine is a 220k exhaust on this car. Not a single leak, BUT The BOTTOM elbow of both CATs on my car are terribly rusty. Deep surface rust. I've been concerned for a while. Should I just replace them?

The CATs these guys are offering on eBay have a much more elegant slope at the base of the CAT as opposed to the near right 90 degree angle at the base of the OEM AND,,, the O2 sensors are accessable from under the car. I LIKE them if they are what is depicted and they actually work...?

150BUCKS!!! These guys have fairly good reviews BUT a strange thing, thier website is down... Facebook seems fairly active though. What do y'all think and does anyone have any experience with them? Was considering calling them today...

Anyone?

https://www.ebay.com/str/canadiancon...is&media=EMAIL

 

Hello All. Good day. Need some help here. And pinched for time (inspections up).

Going back in time a little. Back at this.

So, sometime ago, about 3 months, I went in and replaced both downstream O2 sensors due to the issues described above. Not a bad job at all after removing a bunch of stuff...
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Did a hard reset (not really sure what that means anymore) and have been BARELY driving the car over the winter since.

NO REOCCURRENCE of the p0420 bank 2 cat not performing after sensor change. Slowly watching readiness checks turn green - waiting for p1111.

Yesterday I headed down south on the Jersey shore. Car needs to be inspected this month. Was trying to accomplish the p1111. Car runs beautifully... Would like to to see better mpg, but hey.

TheN CEL!!! This time - Bank 1 p0430. The other CAT is now triggering the CEL. Now I'm pissed and perplexed. This is what I'm seeing.

L and R fuel trims match (basically) in all they do. L and R will climb together, fall together in unison. +/- 1 or 2 points L to R. Rarely if ever over 8 or 9%. LTFT never in the negative,,, STFTs will fluctuating dipping positive and negative - adjusting...

Here's the thing. Say when I am entering the highway, basically anytime I give the ol girl extra gas and want to pick up speed under load - the L and R LTFT drop to ZERO FLAT (never down into a negative numbers - ever!) And then, as I let off the gas (having accomplished the speed I desire) things level out and LTFT will return to 7, 8, 9%. Values they live at during regular driving.

What would cause trims to drop so predictably, in unison and directly to a value of ZERO on acceleration?

I don't know enough about trims to think this thru.
Is it that the signal coming from the down stream sensors is saying that there is not ENOUGH fuel when giving a reading of zero?

 

Fuel trims are not a simple/single number per bank. They are arranged in a matrix, with dependency on rpm and load. Think of the trim as the elevation on a map where the rpm and load are your flat dimensions, so to speak.

As the O2 sensors are not providing feedback immediate enough to directly drive the fuel injectors, the scheme is divided in long term and short term. The long term is the "memory" and drives the injectors. The short term is the more immediate reading. Long term trims are adjusted by the average of 2 minutes of short term readings, for a given rpm and load.

For example, if you have a long term trim of 2 (at a given rpm and load) and the average short term trim (at the same rpm and load) averages 0.1, after 2 min of short term data is accumulated at that rpm/load, the long term trim is adjusted to 2.1. As the ECU has now adjusted fuel by 2.1%, the short term trims from that point forward would likely average to zero necessitating no further changes.

Obviously, the car on a normal trip goes through many combinations of load and rpm. Also, some combinations of load and rpm are visited a lot more frequently than others.

In your example, there is a read at idle. There is probably a different read at idle in Neutral (lower load). As you accelerate, you "travel" the trim matrix through higher rpm and higher load, each having its own set of trims. If you have done a hard reset, the long term trims are likely back down to zero. Maybe there has not been enough time for the short term trims to accumulate and adjust the long term trims. FWIW, zero on the trims means there is no need to adjust the fuel as coded at the factory, in a zero air leak scenario, with an AFM as perfect as it gets.

From memory, the more complete procedure after a battery reset involves not only the window travel thing, but also staying stationary (on the brakes), in Drive, and at 2 different rpms for over 2 min. This is to update the trims for the more popular rpms and higher load for that off-the-line acceleration.

Best of luck, keep us posted.

 

So, what do you think I should do now?

And, how does the weirdness with the trims relate to the 0420 and 0430 CEL saying that I have bad CATs??? That is, if there is a connection at all. Is there?

After any reset I've ever done - I've never seen trims start at ZERO (or any other random number as a "start" point perse) and then slowly work themselves to some other, or some "real" measured value or percentage.

What I have always seen is, after reset (and again, sometimes I question the effectiveness of the reset), is a real and immediate value (what's being read by the sensors at the exhaust) shown as a percent, and over miles and time, the ECU learns and adapts. Effectively getting used to whatever change I've introduced and finding it's new best base line.

Ill go back and reread your post Mertz, but I'm not clear on what you're saying is wrong, or could be wrong. Or what I might do... It's very possible I missed it.

 

Reset trims = (specialist tool or) battery off. (Or fix things perfectly and let the car relearn and they'll be near zero.)

Not an ordinary OBD clear (which isn't a "reset", though it does clear aka rest the OBD monitors).

If the trims are bad fix them before worrying about P0420 etc in case they're misleading.

 

Thanks for the reply...!

In this, are you talking about the usual reset procedure used here, ie contact the positive to the negative battery terminals? If so, while I was changing the sensors on the car, I had the negative and positive battery terminals clipped together (over 24hrs), battery out of the car and the key in the "ON/RUN" position... Is this what ya mean by reset?

I've been tempted to go right to the ECU, remove it from the car, use the wiring charts and ground all and any power leads I can find to zero out (hard reset) the ECU. That, while using the regular procedure on the with battery cables.

Can you think of any reason why I would get a flat ZERO on acceleration and not during regular driving?

Also, other than trim values - is there anything I might be able to see looking at raw voltage values from the downstream O2 sensors (which are new denso units) that will help me understand the condition of the CATs? Which value would I be looking for in the O2 sensor list obd?

 

The strange thing is both CATs behave the same way to the number. On acceleration they both drop to ZERO. The short term trims aren't really doing anything too strange. And, not too too long ago, my trims were great. I was pleased at the difference and the readings I was getting with the install of the "new" 36k mile engine...

What do folks think about Canadian Company ALL STAR EXHAUST on ebay and there super reasonably priced CATs?

 

I can’t comment on why your trims go to zero when you’re accelerating because I’ve never driven my car with the live data hooked up to my laptop. Just so many things can go wrong with plugs becoming disconnected or laptops falling to the floor but I can tell you that in order to get the P0420 or P0430 code you need to have 2 Separate Dr. cycles under your belt where You have been cruising at a specific speed in RPM so that a bunch of engine parameters are in this little short range for a minimum specified time that I can’t recall and if you get a flag on 2 Consecutive Drive cycles, then itll throw the code.

so that’s why it doesn’t show up every time you drive. In my case if I get on the highway a couple miles down the road (which is a long stretch and I just cruise at the same miles per hour) thats one cycle. Once I get to my destination, if I shut it off, but come back home, on the way home I’m driving that same stretch in the opposite direction and that’s when I’ll throw the codes.

but if I do a short trip in between , it’s not two consecutive drive cycles in a row so I don’t get a code. I have thought I had cured my car from those two codes dozens of times only to have it pop back up a month or more later or something. It’s frustrating the hell out of me.

 

I completely understand. Frustrating the hell out of me too! The thing is, as I read thru other forums, other cars, there is and will be a tell tale problem for why these codes show up (mostly) and people can resolve them. Not this car. There is no reason that I have been able to understand that this is happening. Tooooo too much magic and guesswork.

I forgot to mention. Yes, I was driving to get all the readiness codes to go green, p1111. I had 4 to go. "Evap System" - "Components", "O2 sensors" and "Catalyst"... Can you believe of the four,,,, wait for it,,,, CATs and 02 Sensors set as complete, went green, and still CEL and the other two remained. Why would the CATs set as complete with no trouble and still throw a CEL? Maybe it's "designed" like that. In a couple of weeks I'm going to have to park the car in the back yard or get tickets everyday.

I'm willing to do the work (even enjoy it) but don't know what to work on 😬😐😬😐😬

 

That will clear all the learned values, including fuel trims, and also all the OBD monitors (in case you need smog, gulp).

No point at all. Well, you could check no water got in.

It's how OBD II can be. Normal. (During WOT the trims aren't required to be reported.)

Downstreams shouldn't change voltage much, most of the time, but the PCM may deliberately tweak fuel to check they're working and obviously they'll change then.

 

It's quite basic OBD. Read on.

That's normal for OBD. Many codes cannot be flagged unless the monitors are OK because the car literally does not know what to trust so can't figure what's wrong.

I've explained above. Jaguar/Denso/others have documented this in response to the laws of your (& other) countries. If you want, search along the lines of
JAGUAR ON-BOARD DIAGNOSTICS pdf
and find one that applies to your car or a similar Jag

 

220k miles on the cats…you’re not going to fix them they’re done lol

again go commit some big epa violations or slap some cheap converters in there. scrap value of the cats is 1 grand plus