Do I have a bad Cat or Sensor

The main cause of P0420-430 is a faulty cat. The reason sensors "fix" the codes is because the sensors and cat become contaminated. The new sensors work better and ECU has better readings. You will probably replace the front sensor and cat to correct the light. The front sensor buys time but it is inevitable that the cat will need to be replaced. You also want to make sure your not burning coolant or oil that will just ruin the new parts quicker.
Also the cat should be replaced with the factory part. The cheaper aftermarket ones don't have the proper amount of material to function properly and many people get the codes coming back because the cat can't clean the exhaust properly. It is actually illegal to purchase non OEM cats in CA and NY.
My 2 cents of 20 years as Toyota master tech.
 
JKC2638 said:
It is actually illegal to purchase non OEM cats in CA and NY.
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Depending on how you define "non-OEM", this statement isn't exactly correct here in CA. Here's what it says regarding aftermarket cats from CARB's website here:
"Aftermarket catalytic converters must be exempted from California's anti-tampering laws in order to be legally sold and installed in the state. If an aftermarket catalytic converter is shown to be durable and meets vehicle emission control requirements, it is granted an exemption Executive Order (EO) that allows it to be installed on specific emission controlled vehicles."
 
JKC2638 said:
The main cause of P0420-430 is a faulty cat. The reason sensors "fix" the codes is because the sensors and cat become contaminated. The new sensors work better and ECU has better readings. You will probably replace the front sensor and cat to correct the light. The front sensor buys time but it is inevitable that the cat will need to be replaced. You also want to make sure your not burning coolant or oil that will just ruin the new parts quicker.
Also the cat should be replaced with the factory part. The cheaper aftermarket ones don't have the proper amount of material to function properly and many people get the codes coming back because the cat can't clean the exhaust properly. It is actually illegal to purchase non OEM cats in CA and NY.
My 2 cents of 20 years as Toyota master tech.
Click to expand...


Don't tell some of these guys that! They don't want to hear that Toyota is actually pretty smart with their cat codes and how they're triggered. It just has to be an oxygen sensor, it just has to be!!
 
Well it is easier to to start at cheaper fix than go right to replace cats ! Replace back 2 o2 sensors before moving to front a/f sensors . Just saying oem cats start at about 700$ unless you live in Kali who have many salvage yards & where they should go for a replacement (if in Kali) .
 
paperchasin said:
Depending on how you define "non-OEM", this statement isn't exactly correct here in CA. Here's what it says regarding aftermarket cats from CARB's website here:
"Aftermarket catalytic converters must be exempted from California's anti-tampering laws in order to be legally sold and installed in the state. If an aftermarket catalytic converter is shown to be durable and meets vehicle emission control requirements, it is granted an exemption Executive Order (EO) that allows it to be installed on specific emission controlled vehicles."
Click to expand...

Yes, the cat must meet OEM standards to be certified. It is hard for me to trust some aftermarket parts working at the dealer for so long. I have seen many people waste money trying to guess at repairs or buy inferior parts. That is was is great about forums like this, you get a lot of input of what works and what doesn't. There are good aftermarket parts out there. Forums help people make good decisions on repairs and mods.
 
JKC2638 said:
The main cause of P0420-430 is a faulty cat. The reason sensors "fix" the codes is because the sensors and cat become contaminated. The new sensors work better and ECU has better readings. You will probably replace the front sensor and cat to correct the light. The front sensor buys time but it is inevitable that the cat will need to be replaced. You also want to make sure your not burning coolant or oil that will just ruin the new parts quicker.
Also the cat should be replaced with the factory part. The cheaper aftermarket ones don't have the proper amount of material to function properly and many people get the codes coming back because the cat can't clean the exhaust properly. It is actually illegal to purchase non OEM cats in CA and NY.
My 2 cents of 20 years as Toyota master tech.
Click to expand...

Thanks for input.
When I left the house this morning I noticed that the lights are off. Do they reset themselves?
 
cnl390 said:
Nothing at all.
Click to expand...

Sounds like the sensors are marginally functional. My initial assumption of bad cat in bank 2 was based on the data you provided, but generally speaking, catalysts rarely go bad this soon unless you have some other engine problems.

Best bet is to take it to a mechanic with a dedicated scan tool to pull the live data and see how the sensors are reacting. He will typically introduce an external source of fuel (propane) into the intake, causing both of your A/F sensors to react. Based on this, he can also check fuel trim and make a determination on whether or not your A/F sensors are functioning correctly (A/F sensors primary function is to adjust fuel trim to get it as close to stoichiometric conditions as possible).

He should also be able to look at the data from the rear O2 sensors and make the same determination on whether or not those sensors are functioning and at that point, determine if it is indeed a bad catalytic converter.
 
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