check engine light...again

Newbie seeking answers. I have a 2001 Tacoma 6cyl. I bought the truck
with 110,000 miles. The check engine light came on almost immediately.
I replaced the front CO2 sensor. The light came back on. Replaced the rear.
light on. Replaced the cat. Light stayed off for about 2000 miles and now it's
back on. What now?

 

Have you gotten the code read? Do you know for sure it's an emissions problem?

 

Our trucks are not happy with aftermarket sensors or cats. You have a 2001 tacoma so it's rated for California carb emmissions I believe, so there should be two cats. Did you use a denso brand o2 or a/f sensor? What cat did you use?

 

Sensors were toyota parts, although I had a aftermarket cat put on by a muffler
shop. The OEM was exactly twice a much as the aftermarket.

 

I'm about to replace the rear cat and O2 sensors on my 01. I pulled the code my self and got the P0420. I took it to a shop so they could tell me exactly what wasn't working. They said the rear cat and O2 sensor was bad. I'm gonna go ahead and replace both sensors and the rear cat. I've heard a lot of people say that our trucks don't do well with cheap aftermarket cats or sensors. Although, I have heard plenty of stories about magnaflow being a good quality cat. When I do mine I'm gonna go with magnaflow and DENSO sensors. Hope this helps. Good Luck!!!

 

Ditto^^^^^^^^^^^^^^^^

magnaflow is the way to go, I have used them in the past on a stang, with no trouble. very good quality product.

 

I also went with 50 state magnaflow cats, got 10% from autoanything. Seems to be a good quality alternative to Toyota ones. Most aftermarket cats are "49 state" legal, I think every Toyota after 2001 is 50 state legal and won't accept crappy emmission parts

 

OP:
you never mentioned what code it is you're getting
is it the 0420?

i keep getting that too, it's strange, though
i manually reset it once (well, disconnected the battery) and it stayed off for weeks; came back
then, after that, it went off by itself, and stayed off for a couple of weeks; just came back

what's strange is that both times it's came on, it's been in the same exact place;
when i'm heading up the bottom of this specific mountain range going around 35-40 in 4th
could just be a coincidence; but, it's seriously in just about the same exact spot, right down to the blade of grass, going the same speed, in the same gear

 

I'm running Bosch O2 sensors on mine, never had a problem. Plus they are a lot cheaper.

 

Depending on the code your getting, try cleaning MAF sensor. Get a can of MAF cleaner at auto parts store.

 

Idk about bosch, except their spark plugs suck, alls i know is non denso sensors don't work for most people, you're special! I'd rather just go with denso stuff from rock auto

 

Maybe just lucky. That was before I got smart and started using only Toyota or Denso parts for my truck.

 

Auto Zone code reads PO420.air leak in exhaust before HO2S.
Installer

 

Catalytic converter(nevermind it already replaced, didnt see that part)

 

PO420 can mean everything from a leaky gas cap, to a leak in the fuel filler neck, or a leak at the charcoal canister, or a bad converter. I wouldn't be surprised if you replaced the converter and it comes back.

 

I went to the Toyota dealer and had it diagnosed. They came back with bad cat....
2600.00 to replace. Muffler guy who replaced with aftermarket cat wants me drive 125 miles and leave to have diagnosed by his guy. Between a rock and hard place.
The guy who replaced the cat took the truck to his mechanic. He came back with; the cat is good. the problem is with the front O2 .It is switching too slow causing it to trigger the check engine light. so now I have full circle...back to the front sensor. So I replace the front O2 again? Oh and it is still reading PO420.