I’m getting the dreaded catalyst efficiency below threshold error. I’ve read a lot of people saying it’s usually related to a leak just before the cat pipe connects to the mid pipe and hence before the post-cat sensors. But I’ve found tiny hole just after the sensors themselves. So question is will a hole after the sensor still throw the cat efficiency error?

 

Ah man I literally just got this as well. Codes P0420 & P0430. First mechanic immediately pushed me towards 2 CAT cleanings for $1,700 Following and hoping we're both dodge a bullet.

 

What year/how many miles/km on your IS?

Did your IS burn oil before this happened?

 

2007 over 200k and it does not burn oil.

 

Start by getting the pin hoke leaks addressed. Any muffler shop in the states should be able to tack weld the leaks, or replace the compromised pipe. This is probably the cheapest route for troubleshooting. If worse case then the cat is toast, and needs replacing. Another is just a bad reading o2 downstream sensor.

https://www.clublexus.com/forums/is-...is250-awd.html


https://www.clublexus.com/forums/is-...e-exhaust.html

https://www.clublexus.com/forums/is-...-bank-2-a.html

 

P0420 / P0430 codes will get thrown for inefficient catalytic converter when the efficiency falls below 95%. That’s right, only 5% of the efficiency has been lost. You’re now at 94.9% efficient. Do not waste money on a new cats. Google Scotty Kilmer lacquer thinner, his method will solve your problem.


I went to Canadian tire and purchased 4 L of lacquer thinner and dumped it into a half a tank of gas (don’t spill any on the paint) and went for a nice long 300km drive. Don’t clear the code beforehand, let it clear itself. Mine went off in the first 100kms.

The lacquer thinner will clean out your catalytic converter, your light will go off, and stay off for 6 to 12 months. I put a litre in a half tank every 3 to 4 months to keep my cats clean. Stop and go driving in the city is hard on the catalytic converters. Works like a charm. Does not harm your car engine in anyway whatsoever. Google it.

It’s quite an effective cleaning of the catalytic converters if the problem is as simple as soot clogging the cats, which is common. Also, your car will be extremely responsive with the most amazing throttle response. Once you are near empty, fill it up with premium and you’re good to go for a year. 👍

Added bonus, it will de-carbonize the pistons as well. For IS350 owners, it help clean the intake valves as well due to the additional port injectors on our engine.
Good luck. Cheers.

ps, there is also an option to take the downstream O2 sensor and put a spacer on it, such that it pulls the oxygen sensor out of the middle stream of the exhaust gases. That also works to clear / prevent the P0420 code.

 

Very interesting. A clogged cat would be a real pain. If I ever get these codes down the road, now I know what to do!