P0420

The computer reads exhaust gas going into catalytic converter from B1S1
And reads exhaust gas going out of catalytic converter from B1S2. Data determines the fuel trims as well as the catalytic converters operating status. Thus the term " Catalytic converter operating below predetermined efficiency" P0420

 

If you're lucky you can pull the black rubber plug under the passenger side floor and pull the connection out rather than pulling rocker panel cover and carpet under passenger seat.

 

Make sure to get the proper Denso branded O2 sensors and beware of cheap priced fake ones online. These trucks don't fare well with aftermarket sensors

 

only denso one

 

Not sure if that was a question lol, but yes...Denso is the OEM brand for Toyota sensors. A lot of other companies make sensors for these trucks as well but they usually don't work well and you'd likely see the problem persist

 

yea i only get the denso ones

 

eon_blue is right
Buy from DensoProducts online for exact replacement. I've seen sensors that you have to splice the wires and wrong connectors, incorrect wire ga. and length. Even screw in sensors with adapter plates from other than DensoProducts online. Save yourself some misery, pay the extra $8

 

replace the front one first, see what happens......you can always replace the back one later.

 

Front one is brand new

 

Oops.....I missed that.

You were smarter than me. I had code and replaced both, it still came on constantly. Took out new Denso rear O2 and code went off for a long time then finally came on again recently .....finally did the $4.00 capacitor/ resistor trick and now out for months......URD next ?????

 

That's what I will be doing... if this doesn't work then the urd simulator

 

You need a new cat(s) or you have an exhaust leak

 

100% tight exhaust. Cats (California model $$$$$) are slowly dying, exit temperatures are below threshold, probably too much low speed , short hop driving.

Just trying to postpone the major expense on a truck that’s driven 3-4,000 miles a year.

 

I switched to non Ethanol gas and CEL has been off for the last 8 months.
What's in your Tank?

 

The cheap stuff......$2.03 a gallon.

if it eventually comes on again I might invest in some Cataclean or the Scotty Kilmer paint thinner method ; )

 

TruFuel is $20 gal Cataclean $20 pint
Same stuff different pricing.

 

TruFuel......thanks, I’ll write that down so I don’t forget. I’m also old n’ forgetful : (

P.S. I included the $2.03 price per gallon just to tease the California guys ; )

 

I gotcha
Tacomas don't do well on 10+% Ethanol is why I asked what's in your tank

 

I went through this myself a couple years ago, my cats burned out thanks to a lean condition I had with the supercharger because the previous owner didn't do any fuel modifications to accommodate it.

Got the P0420 code and eventually figured out it was my front cat that was bad, needed to pass smog so I could get registered. Called Toyota and they wanted nearly $3,000 to install 2 OEM cats on my truck, I politely said 'F that' lol. I ended up getting two CA approved Magnaflow cats installed by a local exhaust shop. I passed smog after that with flying colors and just recently passed again last month. The Magnaflows were $600 installed, front and rear

I guess my main point is, you don't have to replace your CA cats with OEM cats, you can get CA approved ones in the aftermarket for much, much cheaper. Magnaflow is widely regarded as the best option