Help P0420 and P0430

Check engine light came on and both of those codes came on at the same time.

"Catalytic system efficiency below threshold (Bank 1)"


"Catalytic system efficiency below threshold (Bank 2)"

 

Upstream and down stream Oxygen sensor.

 

Aren't there 4 sensors? Which ones exactly?

 

What's your mileage? If under 80,000 take it to the dealership now!! Cats are covered until 80,000... I missed out on that and had to buy new manifolds.

 

Well wipe out your multimeter to check the current each sensor ... That's how you find out .

 

I'm at 116k on mileage

 

I got the check engine light several weeks ago, read the codes, reset the codes and they came back real quick. I was just about to flip the switch on new cats, but ordered new OEM O2 sensors, then I read about running 87 oc gas. So I fill up with 89 oc gas and in one day of about 50 miles driving the check engine light goes out. So what to think, was cheap gas my problem? Time will tell. I think I will reset the codes in the cpu tomorrow and see what happens.

 

How did you make out with switching gas? No more codes?

 

Hello,

I've been fighting the P0420 code since June (it is now october). CEL came on and brought it in. First they changed the front cat, fine for a 2 days then light came back on. Then they swapped out the rear cat. Same thing, fine for a week or so then the light came back on. They said they changed out the sensors and cleared the code but then it came back again. Finally after talking to the manager, they did a complete change out of everything, both cats and sensors. The sensors are the densos but the cat i believe is still an aftermarket cat from napa. This kept the light off for about 3 weeks, but boom...light came... (btw, the truck is an '04 tacoma with 320K miles...) any suggestions? Do i bite the bullet and get the OEM cat?