quote:

Originally posted by architect:
I'd also add, take a look under the car and make sure nobody has made off with your cat.

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Originally posted by jimmy123x:
Do you ever drive the car hard? IF not, go out and floor the gas pedal everywhere you go for the day, then have the code cleared and see if it comes back.

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Originally posted by rangeme101:
Might not be the cat. Need to do some more testing. See if there is a forum for your vehicle and search for the fault and see what others had to do for the fix. Could clear the code and see if it comes back. <<snip>>

quote:

Originally posted by jimmy123x:
Do you ever drive the car hard? IF not, go out and floor the gas pedal everywhere you go for the day, then have the code cleared and see if it comes back.

quote:

Originally posted by HRK:
How old is the car, high miles?, could be a sensor or the CAT.

Agree with just going to an auto parts store and borrowing the scan tool, delete the code, note it and date it happens and drive on, see if it's real or a phantom code.

Could always cut the cat out and put in a straight piece of pipe if you don't have emissions testing in AL, even though a replacement is best.

quote:

Originally posted by C L Wilkins:
Question for the OP. What brand(s) of gasoline do you use?

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Originally posted by 4MUL8R:
<<snip>>
So, what we know is that the code does not magically go away. We don't know the O2 sensor voltages. To me, checking O2 sensors is the next obvious step.

quote:

Originally posted by 4MUL8R:
Let's review the logic of the error code. Maybe next steps will become apparent?

1. There are two oxygen sensors. One is upstream and one is downstream of the catalyst.

2. The upstream oxygen sensor is the primary feedback for the air:fuel ratio. The computer continually adjusts the injector pulse width to match the mass of air entering the engine. The sensor voltage is above or below what is known to be the correct air:fuel ratio. This signifies either "lean" (too much oxygen) or "rich" (too much fuel).

3. Catalysts affect emissions through high temperature reactions and special metals present on a substrate made from ceramic. In some examples, the substrate looks much like a bee hive honeycomb. Some substrates are also "tortuous path" rather than a more open flow. As the catalyst removes undesirable pollutants, that substrate can become less efficient. If something is terribly wrong, it can become partially clogged. There are special test rigs for catalysts, at special labs, and those labs charge thousands of dollars to evaluate a catalytic converter. I've spent thousands of dollars evaluating catalysts, and the data can be very instructive. However, these tests and the data are for catalyst designers and manufacturers, to validate that the product does as required over the life of the vehicle. The catalyst is covered under the EPA emissions warranty period, which can be longer than the vehicle warranty.

4. Catalyst deposits are not typically removed through "rev it up and go real fast" driving. This remedy was made popular when Smokey And The Bandit was still in theaters in its first run. Back then, catalysts were band-aids, most often located under the vehicle, and about six feet from the cylinder head exhaust port. Cold catalysts do not function well. They do not remove pollutants. They do not get hot quickly. So, catalysts today are as close to the exhaust ports as physically possible. In some vehicles, there is not much space for a manifold, or "header." The catalyst is most often in four-cylinder transverse engines visible just behind the radiator fans behind a sheet metal heat shield. There, you can often see the upstream O2 sensor, and sometimes the downstream sensor. In the V-6 dual turbo engines, the catalysts are just behind the very hot turbo exhaust. The point is that the catalyst must be very hot to do the "catalyzing" with the precious metals, to change the emissions from harmful to not harmful.

5. Catalyst performance is monitored by the downstream O2 sensor. If the sensor reports lean or excessively rich exhaust gas, the computer must then offer an error code. Is the upstream sensor voltage OK? If OK, then why is the downstream O2 sensor voltage not OK? Maybe it is the catalyst. That would be bad. I'd better tell the vehicle owner with a code.

6. O2 sensors can go bad. And they do go bad. Believe it or not, excessive water in the exhaust can harm the sensor. The sensor is also ceramic, and you can't see the sensing element under a ventilated protective metal shield. On that shield will be all sorts of black carbon. But, the O2 sensor itself has some protection. A simple 2-wire O2 sensor downstream of the catalyst can go bad. The logic, though, is that the environment must be protected, so the computer says "check the catalyst."

How can you check the catalyst? Yes, you have to send it to a lab for destructive tests that cost thousands of dollars. For sure, if you look for raw simple blockage, you can put a borescope in the upstream O2 sensor fitting hole, navigate it through the piple, and inspect the catalyst substrate there. But, for most people, partial blockage or full blockage is not a judgement we can make. Some cells can look blocked, kind of like when a wasp next has a dead baby wasp but all the other cells are obviously open. But, the catalyst is several inches long, and you can't see anywhere else inside the catalyst. And, you have to have a borescope camera ($$$$), a lift ($$$), special O2 sensor socket, a solvent to release the super hot threads, etc. Not many of us have these. For me, it was simple -- at the lab we had anything we needed to work on a car -- and we did.

Now, there are obvious performance issues when a catalyst is blocked. The OP reports strong vehicle performance. With a five cylinder engine, one downpipe, one catalyst, a blocked catalyst would be noteworthy. If the OP senses no blockage, due to consistent performance over time, the OP might suspect a failed O2 sensor. You'd think the computer would say "downstream O2 sensor voltage out of range" if it were bad...don't I wish!

One diagnostic method is to change the downstream O2 sensor. But, if you have access to a real OBDII technician grade evaluation box (not a code reader), you can see the O2 sensor voltages. These wander back and forth, all day long, but they do have a generally known voltage range. If the O2 sensors both have normal voltages, and no other issues, then you might wonder about the catalyst. If the O2 sensor voltage is NOT as expected, then a diagnostic replacement might be more affordable than swapping the cat. With a new cat, I would want to change the O2 sensors anyway.

So, what we know is that the code does not magically go away. We don't know the O2 sensor voltages. To me, checking O2 sensors is the next obvious step.