Need Help with P0430 trouble code. (Catalytic converter)

I bet that's a red herring. That code means that the O2 level on the output of the converter is high, meaning the converter isn't working right. That has nothing to do with your original problem.

If not, the catalyst isn't doing it's job. If you have two exit O2 sensors, swap the sensors between the two sides and see if the error moves. If so, it's a bad sensor or bad wiring. If not, the converter isn't working.

The converter not working could be because it's poisoned with junk, but if the problem were because the exhaust going into it was screwed up, you would see the primary O2 sensor out of range also.

No. It'll tell you what value is coming out of the sensor, but you can get that with a multitester. Your question is whether that value is valid or not.

If you have 331,000 miles on the original cat, a miracle has occurred and you should be very pleased with it.

However.... is there any reason you need to replace it? If the vehicle is driving fine and there is no emissions inspection, there's no real reason to replace it right now if it is indeed bad.

--scott

You are not going to get much more info than you already have from a code reader. But a good code reader will be handy anyway. If you have a laptop you can just get a USB/obdII adapter and the software (available on ebay and elsewhere). You will be able to turn the code off, but the code may turn itself off anyway.

the particular code you are getting is due to the built-in diagnostic for the cat. It means the self-diagnostic test that triggers the code indicates the cat is not consuming O2 as well as it should. The cat may be weak or the 2nd O2 sensor may be weak or you may have an exhaust leak or loose electrical connection that is throwing the test off.

The good news is this code usually does not indicate an engine problem if there are no other codes to go with it. In other words, if you had a vacuum leak or misfire or burning oil this code would not be the only indication of your problem.

-jim

Call me anal, but I hate any check engine light on. If the second 02 snesor measures how much 02 is being taken by the converter, I guess taking the guts out of the inside of the converter would cause a code?

I do have an exhaust leak but it is at the muffler, after the cat by the way.

Yes. You did that on only one side?

Yes, it would cause precisely the code you have.

Again, could be a sensor or wiring, or it could be a bad converter. Given the mileage, a bad converter wouldn't be surprising.

I have cleaned gunked-up converters with acetone and had them work well again once the catalyst was exposed again, though I can't recommend that and it may not be legal (even if effective). But it's also possible to have the catalyst just mechanically worn away after enough exhaust has passed through there.

--scott

Is there a way to bypass the converters and somehow fool the sensor into working properly? Autozone has a "universal" converter for 73 bucks for one. I'd rather just do away with them if i could still get the light to go off and for it to run properly.

By the way when it talks about "bank 2" for the code, which converter is that on my 1996 350 silverado?

I appreciate it!

No.

Either fix it or ignore the light.

If you're going to fix it, find out if it's the converter or not before you go swapping the converter out.

Dunno, but the manual will tell you. I suggest, though, first swapping the outside O2 sensors between the two converters and seeing if the problem moves to bank 1. If it doesn't, change the converter after FIRST making sure there are no leaks in the exhaust system anywhere.

--scott

Passenger side

Ok. I will check the o2 after the cat on the passanger side.

One question, if the o2 sensor after the cat just looks for oxygen, what would happen if you left a good o2 sensor plugged in but took it out of the exhaust pipe into free air? Looks like it would read more oxygen.

It seems I read somewhere about replacing the cat with a straight pipe and welding in a spark plug non fouler to "lift" the o2 sensor out of the exhaust stream a little bit

the sensor is looking for not just oxygen content, but how it varies over time. when in closed loop, the computer varies between rich and lean every few seconds. that way, via the primary sensor, it knows where the center point is for stoichiometry, and the cat gets loaded with oxygen to help with the conversion process. with the secondary, it tracks the output from the cat, and whether it's following the input too closely or not. if yes, then the cat's efficiency has dropped below acceptable limits, and it registers a code, which is what you're seeing.

bottom line: if there's a code, then the sensor's out or the cat's out. you can't just have no cat because the computer wants to see the signal difference between the two. first, i'd try new sensors - a slow primary can give problems with too much difference between the two. if you buy online, sensors aren't too expensive these days. if that doesn't clear the codes, get your $77 generic converter, weld it in, and you should be set.

warning: cheap cats are cheap for a reason - their precious metal content is minimal and they don't last very long. when welding, make sure you take the need to repeat the process into account with your pipes and flanges. or buy the much more expensive but guaranteed to last longer factory cat and have it last another 15 years.

Ok. I will check the o2 after the cat on the passanger side.

One question, if the o2 sensor after the cat just looks for oxygen, what would happen if you left a good o2 sensor plugged in but took it out of the exhaust pipe into free air? Looks like it would read more oxygen.

******* Do you think the temperature of cool air versus the temperature of the exhaust would affect the oxygen reading? Bank on it.

I actually have a new after cat o2 sensor I never put in. I will try that. But dang, the oe converter even at autozone is 375 bucks. I want it to run right but it does have 332,000 on it.

I have read online about an o2 simulator??????

in a heated sensor??? or don't you know what all those wires are for? [rhetorical]

what's the point?

step back and look at the big picture context: buying a new vehicle will cost you a chunk of cash down, plus payments and depreciation. any one of which will be more than a new cat/pair of sensors/both. and it'll cost you a chunk more in insurance because you'll have to have the whole shebang, not just liability. repair, assuming the rest of the vehicle isn't too much of a crate, is by far the cheapest option.

I have been told that does work (to eliminate the 420/430 code). The idea is that by getting it into a recess out of the flow of gasses the second O2 sensor will not see the rapidly changing O2 content. In theory this sounds good but I have no personal experience.

-jim

Right, and that would cause the computer to pitch an error saying there was too much oxygen.

Just fix it properly and don't fool around with stupid stuff like this.

--scott

Depends on your definition of stupid. Things he might consider:

Installing a small spark-plug adapter (BTW it shouldn't need any welding) is by far and away the least amount of fooling around he could do to if he does anything to address this problem.

Just doing nothing won't cause any harm to the vehicle. And the problem could even disappear on its own.

Replacing the cat sometimes does not fix this problem (especially when it is a cheap cat). He may also end up replacing the O2 sensor and/or replacing all or most of the exhaust to eliminate all leaks.

-jim

Different makes check the cat operation a different ways. What works on Ford might not work on Chevy, etc.