Thread: 2005 Pontiac Grand Prix GT code P0420

Originally Posted by wstefan20

Good input, and if your car is dumping oil on your cat, then this could be a band-aid, or a fix after you correct the real problem.

According to their website, cataclean is comprised of:
Acetone 10% to 30%
Xylene 30% to 60%
Isopropanol 10% to 30%
and Light Petroleum Distilates

All I'm saying is that this is a CLEANER, and if you need a cleaner for the catalytic converter, you also need to fix why it's dirty in the first place. I'm just not a fan of "band-aids".

Actually it's considered an engineered chemical reactant inducer. There are hucksters selling "refurbished" or "cleaned" converters which several companies market tools using soaps, chemicals, solvents even to run through removed converters. All fake, illegal and potentially dangerous(ie leave chemicals in converter it can catch fire being welded in, or overheat during startup) Cataclean actually forces converter to clean it's self. See converters running at proper temp for long enough can process contamination, but if it's too coated it can't reach reaction temp and continues to get worse. I stuck camera up in pipe of car with damaged piston ( drilled holes and plugged with pieces from back pressure test kit) and you could see carbon deposits, we followed Cataclean instructions, monitored converter temps with probes and then reexamined and converter was 90% clean where as it wasn't restricted pressure wise before but set codes. And was contaminated to about 50-60%. Month later inspected it and you couldn't see any oil contamination. By using this product(and I am very conservative in recommending additives) we saved converter. But if your stuck with shop who WONT install universal unit and OEM style is out of price range a $20-$25 bottle MIGHT allow you some time, kill a light, let it pass for plates/inspection and let you save for higher priced OEM style. Luckily here in Indiana we don't have inspections or "certification" . But now as most exhaust inspections are , if light is off and all monitored tests have ran you pass as OBD2 light/failure sets when computer figures engine/exhaust is outside the 1.5 times FTP standards.ie if computer says passed, it's allowed to go on. Some states allow 1 or 2 to not be passed, if not directly related to emissions like EVAP codes, or EGR which are listed as secondary tests. It's all bunch of crap but we have to live with it. And as a tech if I can help customer by using this product to get by for while I will use it till it proves to be detrimental, which is what many of the "YouTube" fixes turn out to be.

Well after about 200 miles the light is back on......same code. I guess a new cat will be put in. What do I need to to look for to see why the cat went bad? I mean the car has almost 130,000 miles on it. Is it possible it could have just been used up by that point? It is the original cat? The car seems to run great, and gets good gas mileage. Doesn't use hardly any oil at all....Its lucky if it shows a tiny bit below the full mark, but still in the good by the time it is ready for an oil change. I hate to replace the cat and have it go bad again.....so any advice would be great. Thanks

Don't listen to the above then, your cat isn't contaminated, it's just depleted. No fixing that except replacing.

If you want to be extra sure, you could get a infared thermometer ($30 harbor freight) and measure the heat with the car running. when at temp, it should be hotter after the catalytic converter then before on your exhaust. This is because of the chemical reaction taking place gives off heat.

Cats going bad is an issue on our vehicles to begin with. I've seen cats go bad around 100,000 miles. 130,000 is about the sweet spot to get a new one anyhow.

I'd pick up a good quality one though. Most of the cheap weld in ones are garbage. I think the walker ones are ok according to a few people here. Hopefully someone has more input one the brand.

Direct bolt in, non carb compliant ( generally ok for non call cars) #54752 $250+ tax/s&h, carb compliant weld in #82618 (Cali ok) $195+tax/s&h,#93253 weld in non carb compliant $95+tax/s&h
This is from NAPA, and all their stuff is Walker or Bosal, I listed Walker #s. Good luck. Most good shops should not charge over 1-2hr labor plus gaskets. Honestly direct bolt in would be my choice, ie better fit. And you can bolt in your self if you can remove bolts/O2 sensor.