A few days ago, I had my mechanic do a fuel induction service, oil change, and a transmission fluid drain & fill. He told me that my car was in excellent shape and drives like brand new. Now my CEL is on and I have code P4020 for bank 1. The Auto Zone employee told me this means 1 of my cats went bad. He also told me that my car should have lost power but I have no power loss and my car is driving perfectly fine. So fine, that I didn't even notice the CEL came on. What's going on?

 

Most likely, the DTC you have is P0420, not P4020. This DTC indicates that your bank 1 catalyst system efficiency is running below threshold. Typical causes for P0420 include a bad front catalytic converter, exhaust pipe leak, or bad oxygen sensors.

Is your CEL flashing or staying on steady? Catalytic converter can be damaged by excessive un-burned fuel being dump into it, which will increase the operating temperature beyond design limits (750-800°C). This will melt the substrate. Some fuel additives and injector cleaners can also damage the catalytic converter. You can try disconnecting the negative battery cable for a few minutes to reset the ECM.

 

You're correct. It is P0420. My CEL is staying on steady. I'm going to have my indy take a look and see what's going on.

 

I did my passenger side front catalytic converter. About 6 months later my drivers side front gave the warning light. I reset it with my code reader and it has not come back on after 1 month. When it comes back on again, then I will reset again. When the code comes on quickly, that is my signal to replace.

A $15 code reader is a tremendous item to own. Plug it in. Read the code/codes. Research. Clear if you want to test the system or wait for re-occurrence.

 

Just heard back from my mechanic. He confirmed that the catalytic converter went bad. Quoted me $550 for parts & labor to replace. Either way, I will invest in a code reader. Thanks everyone.

 

Lex---I'm not rejoicing in your demise but $550 for the cat AND labor is really inexpensive for that job.

I'm not saying your mechanic is trying to pull a fast one on you, but if I were you, I'd reach up under the vehicle with your smartphone and flash on, and snap several pictures of the old cat. Why? Because I have a skeptical side, and your situation is making my spidey-senses tingle, and I'm imagining they might not actually change the cat. Seriously, how many miles do you have on the LS? I think you mentioned when Momma was driving it, the CEL came on, but I don't remember if you said it was flashing or steady? Didn't you tell her to pull over and shut it down, and you had it towed to the repair shop, if I recall correctly? If indeed the CEL was flashing, the cat might be damaged requiring replacement, but if the CEL was only on steady, I'd find it hard to believe your LS has a bad cat, especially if you have less than 200k miles?

At the end of 2017 I also had a CEL come on. It's still on actually. My code was P0430, the PASSENGER side efficiency. I was sweating bullets that I needed the cat replaced, and I posted on here. Many people suggested an exhaust leak. I wanted to believe them but didn't because my LS sounded as quiet as usual. Then one cold winter day I started the LS, and I saw the exhaust condensation/smoke not only coming out of the tailpipes, but from UNDER THE CAR! Under the passenger door was some light smoke!!! I crawled down on my knees and looked up and the smoke/condensation was coming from THE GASKET after the cat, where it meets the exhaust pipe!

So------what I'm saying is, try probing or asking the mechanic, and imply that you know that a LEAK will cause that code that you currently have. Don't get me wrong...you might have a bad cat, but in my case, and many many others, the code was caused by an exhaust leak. Below is the thread documenting all what I just described....

https://www.clublexus.com/forums/ls-...p0430-cel.html

Good luck, and keep us informed!

 

Would this mechanic be the same one that performed the "Fuel Induction Service" on your car? Do you know exactly what the service entails? Excessively rich fuel-to-air mixture will not combust completely in the cylinder. Un-burned fuel will travel to the catalytic converter, overheating and melt to catalyst within. You should also inquire about any cleaners used for said service and make sure they are safe for catalytic converter.

 

@LS430inDE I thought $550 was really inexpensive too. I was expecting $1000 plus. Like you said, something doesnt seem right and I was going to call them in the morning to do some probing. I will definitely look over your thread and ask about the exhaust leak. Also, he told me the cat was bad but didnt suggest a replacement. He said it's safe to drive but won't pass emissions. Since I have an emissions test in a few months, I said let's just replace to get it out the way.

My LS has 164,4XX miles. When my mom was driving my car, the CEL was on steady then it started flashing. As soon as it started flashing, I had her shut it off and it got towed to the Toyo dealer. Currently, it is on steadily again.

Every cylinder on bank 1 was misfiring about 6 months before I got it due to a bad OCV. Then a few weeks after I bought it, it misfired at idle on rainy days and a PCV valve replacement cured it. Then ignition coil 7 went bad shortly after, causing more misfires. Days after replacing that, all the bank 2 cylinders misfired when my mom was driving (another bad OCV). For the last month, no more misfires until it got rainy again and started missing at idle. The fuel induction service stopped the misfiring but broke my cat lol.

@rkw77080 Yes, same mechanic. It was a BG Fuel Induction Service. From what I remember, it cleans the throttle body, fuel injectors, and a few other things. He told me I didn't need this service but I asked him to do it anyway because the Toyo dealership master tech said my throttle body had a lot of carbon build up.

 

That's going to be a close call. The flashing CEL will undoubtedly contribute to a shorter life of the cats, but who knows just how MUCH life the flashing has cummulatively taken away from the cats. Best case scenario, it IS your cat, and they are doing it for the low price of $550! And all your troubles will be behind you! I'm pretty frustrated that you're having frustrations with such a notoriously reliable car!!!

I quickly just looked at various prices for cats, and they range anywhere from the low $100's to several hundred bucks, so it's quite possible they're doing it for $550! Here's a link to pricing cats. Of course, none of these are Yoda/Lexus, but hey, I'm sure they'll work fine! http://www.discountcatalyticconverte...&Ns=price3%7C1

 

Good point. I did some research and my car did have some symptoms of a cat going bad (rotten egg smell every now and then and intermittent rattling on acceleration until the engine warms up). I'm thinking something used in the fuel injection service may have caused it to die off quicker, if it truly is the problem.

Thanks for the link to the cats pricing. I read your thread and I'm definitely going to have my mechanic check for an exhaust leak today. Hopefully this is the last of my problems. Each time I keep being told, "Your car is in excellent shape. It doesn't need anything else." Then I'm back to square one. Right now, "the world's most reliable car" looks like it is on the way to overtaking my Passat W8 as the least reliable car that I've owned lol.

 

Be warned - aftermarket cats won't flow or last as long as OEM. When I got my cats replaced on an 1LS with aftermarket Walker ones to pass smog, I noticed a drop in performance. You live in an non-CARB or OTC state and federal-compliant cats don't have the same amount of precious metal in the washcoat that does the catalytic breakdown of HC/CO/NOx to O2/CO2/N2. Cheaper but you'll be doing the job again next time you get a P0420/P0430 or fail any mandatory emissions testing.

Cars are only as good as the maintenance they get but there are also engineering issues as well.

 

The service advisor told me that the cat he ordered is OEM. Perhaps it is used. I don't see how else it could be $550 to replace.

 

I'll chime in...and take this FWIW.

Did a fuel service treatment on my other LS once. Within a short while, like you, I got the exact same code.

Turned out it was the O2 sensor, and not the cat.

I have no idea if this was just coincidence or other....but seems odd we both had a fuel treatment and within a very short while we got the same code.

 

That's pretty expensive for just 1 cat. Your car has twin cats and a third going towards the muffler. If one of the twins goes bad, the other will soon follow.

I replaced my driver side one and soon after got a code p0430.

 

Back with an update. My mechanic looked over my car thoroughly and couldn't find any exhaust leaks, bad 02 sensors, or anything else. Everything has been good so far except the Check VSC light comes on as soon as I start driving. I will have him address that Monday when I drop my car off for the 90k mile service.