Catalytic Converter Issue

I have a 2008 Tundra CrewMax Limited with 180,000 miles. I replaced the complete exhaust system last Feb 2019 with MagnaFlow Direct Fit driver and passenger side cats plus muffler and pipes - all purchased from AutoAnything. Six months later (Aug 2019) the passenger side cat failed (engine code P0420) and with a lot of back and forth calls and emails, MagnaFlow replaced the cat. Now its 6 months after that and again the replacement cat has failed and I'm getting the same engine code, P0420. MagnaFlow sounds like they are trying to refuse to replace the cat again, saying its probably a cylinder that's overheating which is causing the cat to fail. Can anyone tell me if this is a valid problem or are they BS'ing me? If an overheating cylinder is a possibility then what do I do to fix that? Any recommendations for a different brand direct-fit cat? I live in NY so needs to be OBD II compliant.

Thanks for any help / advice anyone has to offer!

 

I had the same code pop up on my jeep wj when I installed a k&n cold air intake kit. I’d assume it’s not your cat that’s bad, it’s the excess air flow from the entire exhaust system causing the code. The “fix” to my jeep throwing p0420 code was to install a spacer in between the 02 sensor (throwing the code) and the pipe, essentially pulling the o2 sensor from the direct exhaust stream and more towards the edge.

another member was having similar issues recently after installing new exhaust and I offered the same advice. Try using the search feature in top right corner (magnifying glass), maybe he has more info...

 

I have seen a bad O2 sensor cause that code too. Did you look at the voltage output of the O2 sensors and measure the temperature of the cat inlet vs outlet to make sure it is the cat? If the cat is indeed bad I would look at something else causing 2 cats to fail. I would think that even a crappy cat should last longer than 6 months unless it is overheating or getting contaminated.

 

Over in the Celica forums going aftermarket cats fail pretty often. Its often better to spend the extra cash and go OEM. It doesn't mean you can't pass smog which is the same cycle I go through on my Celica on a yearly basis, over the last 7-8 years, I reset the CEL drop 5 gal of gas in the tank and drive it for 5-10 miles before taking it in for smog and it passes every time. I do have an obd 2 reader, and I have logged exact miles before the CEL comes back on. Is it a hassle?, Yes, but sometimes good enough to save the $1500 for a new cat, I'll most likely buy a new cat once it stops working completely ending the pre-smog cycle, eventually. Hope this helps

Edit: BTW I live in CA.

 

Do you have an Android phone (I'm sure there's an app for the iPhone too)? You can download an app called Torque (most likely others but that's the one I have) and get a cheap bluetooth adapter for the OBDII port. With it you can monitor the voltages of the O2 sensors. The upstream one will slowly go up and down while the downstream one will stay flat, above a certain value (I think it was over 1 volt or maybe 1.2 volts) once hot.

Often with the aftermarket cats they don't get as hot as the original ones. It could be they are too far away from the heads, the headers (if you have them) loose too much heat, or they aren't as think as the originals and don't have enough mass to stay hot. Checking the temps could help but if you don't know what they should be it's probably not going to help much without asking someone else to check theirs. You could try wrapping the pipes all the way down to and including the cats.

Or you could just fool the downstream O2 sensor to test if the heater is bad. Because the heat from the engine takes some time to get down to the secondary O2 sensor a heater is added to them. It heats up so the engine can run optimally quicker. Often the primary O2 sensors will have them as well unless they are very close to the head. With the Torque app you should see both of the secondary O2 sensors operating very similar. If not then I would suspect the heater. With a little electronic trickery you could just make it so a voltage level above what's needed is always being sent. This only works with the secondary O2 sensors.

On my 2000 Tundra one of the secondary O2 sensors went bad. Because of the way it failed (they have 4 wires, 2 of which are a heater) it was always reading a voltage. When I said the voltage reading was flat it's not exactly flat. The bad O2 sensor flat as a pancake and was always reading a little over 2 volts, even when the exhaust was cold. But the truck never threw a code because I think the computer only looks for the voltage to drop below a minimal amount. This was a number of years ago so my numbers could be wrong.

 

Usually I don’t see cats fail that fast unless they’re being filled with unburnt fuel or oil. I don’t necessarily blame the manufacturer on a double failure. What weight engine oil are you using? Is your truck burning oil? How old are the spark plugs? How old are the rear O2 sensors?When the old and second cats came out were they rattling? Was there any damage to the shipping container on the new cats? Have you run a can of SeaFoam p/n SS14 through the engine to clean the valves yet? (That shit is really awesome and works wonders) I could be wrong, but you need to do some checking before you blame the manufacturer on this.

 

I have oil changes done at my local Toyota dealer, not sure what weight oil they use. Truck does not burn any oil, spark plugs replaced by dealer at 120,000 miles, O2 sensors were replaced last yr when I put in the new exhaust system (used Denso OEM sensors), no rattling in cats of any kind - passenger cat was cracked, that's why I replaced the system, no damage to shipping box. I'm a nurse so not too mechanically knowledgeable but I will look into the SeaFoam. Thanks for the help!

 

Sorry it's taken so long to reply, work has been crazy. I took your advice and bought a $25 O2 sensor extender and it worked perfect! Turns out it was my fault all along, I live in NY so bought a NY compliant cat (seems logical, right???). Well it turns out Toyota runs California compliant cats and that's why it was failing. Fortunately the extender worked and it saved me from buying another $700 cat! Thanks again!!!