While driving work yesterday, my car (00 ES300 with 135k miles) came with CEL & TRAC OFF. So, I took it to Autozone and got the code - the infamous p0420. Read all the posting in CL and toyotanation forum on p0420.

Evening took the car to Toyota dearler to do further diagnoses to cat. covertor or oxygen sensor needs to be replaced. Since they are busy with recall fix, did the scan to confrm the code and scheduled the service for Thursday. On the way back, picked up Seaform at walmart and poured one can into gas and filled it.

Drove home - 10 miles. Today morning took the car to my daughter's day care center - got the same CEL and TRAC OFF. After dropping her, started the car again to see CEL and TRAC OFF are gone !.

Questions:
1. Why did it show up for a day and gone today - it is normal to behave that way for any cat or oxygen sensor failure?
2. Could seaform might have fixed the issue?
3. Should oxygen sensor be replaced at regular interval - maintenance item?. If so, when?.
4. How could I prevent such failure in future?.

Thanks.......

 

the oxygen sensor is a normal maintenance item, like spark plugs. It's a shame that people resist changing them. Perhaps it's due to their price.

satiger, replace any [upstream] 02 sensors that haven't been replaced yet, except for downstream-- only replace the downstream sensors that are actually out of spec. At 135K miles, you're only about 50K past due.

 

Thanks Ilcoolpass. Ok then I will go with upstream O2 sensor. How many sensors are in upstream & downstream?. Would the labor cost be same if I go with up and down stream at the same time?.

 

2 and 2. unless you have cali, then I think you will have more downstream.

labor will be per sensor, nothing combined.

L L C o o L P a s s

 

Are you willing to hop under there and do it yourself?

Westside Lexus in Houston quoted my father $490 to replace ONE oxygen sensor. And it's the one right on the manifold, right when you open the engine bay. I replaced it without needing to get under the car, in about 3 minutes. It's just a simple "wrench off the old one, wrench on the new one." You'll save a TON of money doing it yourself. Surprisingly, Amazon.com has good prices on the O2 sensors.

 

I have a 98 Calif. ES300 and I had two upsteam, 1 on each exhaust manifold and one down stream, post cat. I was able to replace 2 of 3 sensors. I replaced the one facing the front of the car on the exhaust manifold and the post cat. sensor underneath the car. I could not reach the one near the firewall on the other exhaust manifold and took it the part to the dealer to install and charged me $100.00 in labor to install it. The senors are expensive, each one was about $135.00.

 

Yeah, these sensor are damn expensive. I ordered two front sensors from Amazon for each $123. That is Denso OEM part. Regular price ranges from $170-200 per piece!.

 

Denso O2 sensors for federal emission ES 300s are down to $50 per now on rockauto.com...