mpac

Hello Everyone,

I had my catalytic converter stolen out of my driveway and replaced. There is now a p0171 CEL showing. It was reset but now it's back. There was some doubt whether or not the truck needed the "California Emissions" cat when it was replaced. A standard cat was used per the owners recommendation. I wanted to go with the Cali cat.

My question, do all California emission trucks have two cat's (I think I read this somewhere in earlier threads)? Mine has (had!) one, therefore a standard cat should work, right? The shop had a hard time determining this for some reason.

Would you clean the Maf, check the o2 sensors first and for vacuum leaks or just assume the CEL was a result of the new cat as it had not thrown one before the new install?

They are willing to remove and replace with the more expensive cat with me picking up the difference and not having to buy a whole new one. I'm out another $225.


thanks!

mt_goat

If the cat was insufficient you would get a P0420. No, not all Ca vehicles had 2 cats, it depends on the year (info you left out of post, along with engine, and your location).

mpac

The info on the truck is the 3.4 liter engine and it's a 2000 4x4. Thanks for the info on the cel code. Is everyone else in agreement that it is not the cat? I found a sticker under the hood that says it is in compliance with emissions in every state but california soooooo.... I assuming it's not the cat as well. The coincidence is what bothers me though. Cel light right after cat install.

Any ideas? Gonna clean the Maf this weekend.

Thanks!

toy_tek

was the O2 sensor wire damaged when the cat was stolen? If cleaning the MAF doesn't fix it, try swapping the O2 sensor with another truck and see if you still get the code.

I had a nagging 0171 code for awhile, check your entire intake for any sign of a leak.

Evilmunkey

p0171 is system too lean, myscantool.com has a DTC database plus I use their program w/ my netbook.

b0n3mast3r

well it could be an o2 sensor i replace and nomore po171 but at 100 dollar a piece kinda pricey

99SR5

iTrader: (1)

could be the cat. make sure you get a toyota cat because an aftermarket one can effect toyotas, same with O2 sensors.

mpac

So I have two opinions. One is the cat, the other is not. If it is the cat, do you think upgrading to the "california emissions" cat would fix it. It supposedly has more platinum in it for scrubbing the exhaust.

Can someone explain how it is the cat? Is it because the delta between the two o2 sensors is now out of whack?

mt_goat

I'll repeat in case someone missed it, the ECU will tell you if the cat is not up to par. OBDII code P0420 is what will show up. I agree that the Toyota ECU is very sensitive to cat efficiency and aftermarket cats. But have you gotten a P0420? I will admit I don't know what code (if any) would show up if a cat was clogged up and restricting flow, maybe that is something to consider.

mt_goat

Here's what the FSM has to say about a P0171 CEL:

http://www.ncttora.com/fsm/1996/SIL/...e/cip0171p.pdf

Note the possible trouble areas:

mt_goat

This seems the most likely cause to me, someone ripping out your cat I'm sure wasn't very careful with the sensor wiring harness if it was in the way.

flyingyogi

I love those netbook code readers. Makes it to easy to determine which o2 sensor is bad. Plus the ability to read all the other sensors.

flyingyogi

I agree with mt goat, check the wires on the o2 sensors and then the welds on the new cat for an exhaust leak.

mt_goat

I'm sure an exhaust leak would have to be before the A/F ratio sensor (front O2 sensor) for it to effect the A/F ratio. The cat is behind the A/F sensor (or should be if they installed it right).

Just before the cat on the 2 cat models:

mpac

No other codes except the p0171. Seems it is not the cat then. That will save me 200 bucks for the upgrade from the current cat they installed. I'll start going through the list from mt-Goat (thanks!) and re-post my findings for the next guy. Thanks for all the help everyone!

pineapple

My wife's '99 taco w/3.4 recently pulled the po171. I changed the air filter (looked somewhat clogged), cleared the code and it's been good to go for a couple hundred miles w/o the po171 returning.

mpac

Update,
I cleaned the MAF by taking it out. The front sensor was black. After cleaning it was silver again without any deposits at all. After installation and clearing the CEL, the Truck ran so much better. The light has not come on after about 50 miles. Cross my fingers that it stays off. Thanks again for all the help!

anthony88us

if you put an aftermarket cat in a california emissions 2000 4runner, will it throw a code? i want to bump up the exhaust size from the manifold flange back from 2" to 2.5". and of course i will put the o2 sensors back in before and after the cat. thanks