The "service engine soon" light came on.

The Mans code reader said that the Cat is prompting it.

Will a bad cat affect milage, performance, or other parts of the engine?

(04 Buick LeSabre, 83,000 miles )

This message has been edited. Last edited by: bendable,

Yes, but probably because it's an O2 sensor, not the cat itself.

Post the code

When I had my 2003 Honda Pilot, I started getting the service engine light around 275,000 miles.

Our local mechanic told ,me it was the catalytic convertor that was sending the code.

He said the convertor was likely just worn out and replacing it was the only way to make sure the code would not be sent.

With 275,000 miles on it, I asked what kind of problems may arise if I ignore it?

He said my Pilot was polluting Mother Earth more than legally acceptable, according to emissions standards. he said it could affect my performance as well.

He cleared the code then and again 4 or 5 more times.

I donated the car when I reached 335,000 miles.

I could not personally detect any drop in performance, so I guess I was polluting more than I should.

He offered to replace the convertor, but said he would not replace it if it was his car.

Sorry , I don't know the code.

Had the cat code on my ford escape, ordered new one with o2 sensor and was out about 250.00 from Rockauto. Found a mechanic with torch and paid him 60.00 to install new one. Muffler shops quoted me about 800-1200 dollars to replace. Since we have inspections here I needed to replace it to pass emissions. Code never came back.

I’ve got a bad cat on my V8, ‘07 4Runner. My plan is to replace the entire exhaust with a Magnaflow kit. It’s currently at 237k miles with the engine light on also

Your car has two oxygen sensors, one upstream and one downstream from the catalytic converter. Those sensors analyze the amount of oxygen in your exhaust before and after the cat, and if the computer doesn't see what it expects, it throws a code. More likely than not your Cat is just worn out and not extracting as much pollutant as it's supposed to, but it could also be plugged up and restricting airflow through your exhaust. If that were happening you'd see decreased performance, reduced fuel economy, and maybe even overheating if it's really bad.

If you live in one of those stupid places that has emissions inspection, you aren't going to pass until you get it fixed. I'd probably fix it anyway, just because it would annoy me. But if you're not seeing any performance or fuel economy issues it's probably not going to hurt anything to let it go for a while.

Three things contribute to a cat efficiency code.
Exhaust leaks.
Bad cats.
Bad o2 sensor.

Sensors generally have three kinds of failure.
Shorted high (open circuit) shorted low (shorted to ground) and stuck in range.
The first two are electrical faults and will give o2 sensor faults.
Stuck in range will trigger a cat fault.

A quick way to check the cats is to get the engine up to operating temp and run the engine at 2,000 rpm.
Using an infra red temp gun check the temp of the cats at the inlet and outlet.
If they are working the outlet will be hotter by a couple hundred degrees.
If the temps are about even then it's bad.

I just went through this with the truck.

Both cats were bad, so I replaced them and the sensors. It's fine now.

No emissions testing out here in the weeds

Remove the cats and install o2 sensor simulators.
The simulators are less than $50

quote:

Originally posted by powermad:
Remove the cats and install o2 sensor simulators.
The simulators are less than $50

Where? I couldn't find any as they are illegal.

Drive it and don't worry about it

Time for headers and side pipes.

quote:

Originally posted by Mars_Attacks:

quote:

Originally posted by powermad:
Remove the cats and install o2 sensor simulators.
The simulators are less than $50

Where? I couldn't find any as they are illegal.

Here's one type, basically just a little cat.
http://www.bigdaddiesgarage.com/mini-cat-cel-fix.html

I've seen others in the $25 range.
You only need to fake out the rear one.
The front one is needed for fuel trim.

There are others that plug into the connector and give the required 0.5 volt reference signal, which is all the ECM is looking for.

Don't just leave the cat in there.
Either rod it out or straight pipe it.
They will eventually plug up and start chunking out like Mars did.

I should add that simulators are for offroad applications and such.
So if you um, need one for your sandrail that's ok.

Or rod out the cats and ignore the light.

Yes it can do all of those. Given the cars age, low mileage, and type of car, I'd take it out and run it very hard for a few hours, floor it getting on some highway on ramps etc.......see if you can get the CAT up to temperature and clean out all of the crap thats inside of it.