Catalyst System Efficiency

[1999BlueTahoe]

Good morning and thanks for the add. I just picked up a ‘99 Tahoe 4WD and of course it needs a few things. I’m quite certain it needs shocks and will be taking it to the shop to have the steering/suspension stuff checked out. It doesn’t clank or make any noises, just rides really soft.

The question I would like to address here is the P0420/430 codes. I have always been a Japanese car person and have never dealt with codes about catalytic converters. I am pretty certain that one of the previous owners did some exhaust work and deleted the cats. I think this because the truck is pretty loud but sounds good IMO. Is there any good reason to put cats back in and if so, what are my cat options? I can’t seem to find any universals online for the Tahoe and my local muffler shop wants about $250-300/per side. Also, do these trucks have codes that are specific to the o2 sensors? I would think there shouldn’t be any air/fuel mixture issues with the lack of cats if all the o2 sensors are working. Thank you.

 

[OR VietVet]

Welcome to the forum from Oregon.

The cats are there to do this: A catalytic converter is an exhaust emission control device that reduces toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction (an oxidation and a reduction reaction).

The oxygen sensors are there to help the cats do their job. The upstream sensor reads the exhaust mix before it goes in to the cat and will trigger a DTC if the mix is messed up. The downstream sensor is there to see how good a job the cat is doing. Sensors that are bad can damage the cats and so can inefficient tune related components as well as malfunctioning fuel system controls.

I personally see no reason not to put the cats back on and have good working sensors to help keep the atmosphere from getting dirty.

 

[1999BlueTahoe]

Thank you. I definitely understand the function of the cats. I’m not opposed to putting ones back in but it’s fairly low on my list due to my county not having emission regulations. One of my main goals is to eliminate my three CELS, the two for the cats and the C0221. I’m really trying to only put about a grand into it, aside from the cost of snow tires. Figure shocks are gonna run about $400 installed and still not sure about what will need to be addressed with the rest of the steering/suspension. If there is no harm to be done to the truck by not having cats, assuming o2 sensors are working, then it will be something that has to wait a bit. My first goals are making sure that drivability will maintain for a while and this truck will not be a daily driver. Do you know of some good universal cats that aren’t too expensive?

Welcome to the forum from Oregon.

The cats are there to do this: A catalytic converter is an exhaust emission control device that reduces toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction (an oxidation and a reduction reaction).

The oxygen sensors are there to help the cats do their job. The upstream sensor reads the exhaust mix before it goes in to the cat and will trigger a DTC if the mix is messed up. The downstream sensor is there to see how good a job the cat is doing. Sensors that are bad can damage the cats and so can inefficient tune related components as well as malfunctioning fuel system controls.

I personally see no reason not to put the cats back on and have good working sensors to help keep the atmosphere from getting dirty.

 

[OR VietVet]

I don't have recommendations for universal cats. The downstream oxygen sensor cannot work correctly with no catalytic converter in front of it.

 

[George B]

You can have the rear O2 sensors turned off with a custom engine tune like one from Black Bear Performance.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics, please.


Regarding cats, I have not looked into the legalities for having functioning cats in place for at least a few decades. If I'm not mistaken, back in the day, to willfully operate a motor vehicle on a public road without cats installed, if they were OEM equipment, was a serious federal legal offense, resulting in fines up to $15,000. Perhaps, over the years, these legal requirements for cats for driving on a public road have been reduced or eliminated.

 

[George B]

You should look and see if the cats have in fact been deleted. These trucks are also know to have cat failures that cause these codes. I had one such failure.