would long tube headers cause code po 420

i have fought code po 420 every year. i replaced the whole exhaust last year hoping to fix it. it went off for like 2 weeks and came back. i have LCE long tube headers on the truck and dont think the engine was tuned for them. the headers were on the truck when i bought it. would a tune make a difference.

 

Exhaust manifold gasket leak at the head, maybe

 

i did replace that last year when i did the exhaust i bought a new header since the old one had a hole starting

 

Start replacing dry rotted vacuum lines

 

i have not looked those over will check on them. hope its something simple like that lol

 

Do you have the factory converters installed? Factory 02 sensors?

If the sensors are working and there's no air leaks before or after the engine the cats could be bad

 

i bought denso 02 sensors and its a single cat i replaced that last year with a after market one that was not california compliant to save some money

 

It's likely the cat is not performing well enough to please the obd2 standards.

only way to check is to graph o2 voltage with a scan tool.

 

my friend has a scan tool what should it read for the voltage he thought it was low last year when he scanned it but when we looked it up it seemed within the correct amount i cant remember what it read tho

 

I'm not that familiar with the Cali variant, but do you have that one? I was pretty sure they had dual cats or something wacky

 

That's probably why. The cheaper aftermarket cats have way less of the valuable material in them to filter the exhaust so your O2 sensor is likely reading it as inefficient catalyst

 

i believe i do have the cali variant truck at least the sticker under the hood says so and my truck only has one cat on it i know alot of them have 2 but i dont believe thats the problem

 

If you're sure you don't have an exhaust leak from the headers install then you probably need a better cat converter if you want the code to stay away. Otherwise, just gotta live with it (assuming you don't have smog checks in your area), or do the spark plug fouler mod to trick the rear O2 sensor into thinking the cat is working properly.

 

URD used to sell a rear O2 sensor simulator that would trick the ECU into ignoring the p0420 code but they removed it from their website.... probably got a letter from the EPA or something

Might be able to find a used one somewhere

 

i dont have smog but live in NY so the yearly inspection makes the code and issue i will look into the spark plug fouler mod before biting the bullet and getting a cali cat i am pretty sure i i have no leaks but will check again

 

I have pretty much same setup as yours.....new generic stainless headers....
all new walker exhaust system......and a new JC whitny level generic cat....

I have zero problems......mines cali 2.4l....single cat.......

I would look elsewhere........


There are many things that can cause the P0420 trouble code in your Tacoma. Here are the most common ones.

• Oxygen Sensor– The P0420 codes is thrown when the oxygen sensors on both sides of the exhaust have very similar readings. When the oxygen sensor is bad, it can cause a false reading and trigger the code. If the engine does not exhibit any of the decreased performance associated with a bad catalytic converter, it very well may be the oxygen sensor (if you haven’t noticed the performance loss yet).
• Catalytic Converter– A catalytic converter is responsible for scrubbing out as much pollution as possible from the Tacoma’s exhaust. Over time, they can become clogged. Although, modern catalytic converters are supposed to last the life of most vehicles, it could be there is some underlying problem if it has clogged.
• O2 Sensor Wiring– Over time, the oxygen sensor wiring can go bad. It is especially volatile since it is right next to the hot exhaust at all times. The downstream oxygen sensor wiring is especially volatile since it is so far from the ECM (more distance to travel.
• Tacoma Timing– If your Tacoma is misfiring or the exhaust timing is off, this can affect the gasses that are actually going to the O2 sensors enough to cause the P0420 code to register.
• Exhaust Leak– If there’s a noticeable exhaust leak coming from the vehicle it can change what the O2 sensors register enough to throw the P0420 code.
• Engine Temp Sensor– If the computer doesn’t know what the engine temp is it’ll keep the fuel mixture rich. When the fuel mixture is rich, the exhaust the O2 sensors see will be out of range and it could throw the sensor.

 

For me I'd always replace the ect sensor on back on engine if unknown age...
and then maybe every 50K or so....the sensor tip disintegrates from hot coolant over time...

 

the only thing on your list i have not checked is the temp sensor never replaced it before and when i pulled my plugs last year and replaced them it did seem to be running rich so that could be it

 

I cant help but what did you think of the sound difference going to headers?

 

personally cant say much about the difference had the headers before. just replaced them b/c the NY salt had ruined the old one. for the sound i like it thats why i did get a different one to replace it.