faulty air fuel sensor

[tcpoob]

2005 4WD V6 , less than 15k

on the way to work today, i noticed "check engine" light was on and also on was a few other lights "vsc off", "trac", ... Dropped it at the dealership nearby who just called to report it's caused by a 'short' air fuel sensor.

0.
is the root cause they identified "reasonable" - supposedly it should be easy to identify with "check engine" light on, they should be able to plug the OBD computer and read the "log" or something, right?

1.
I am guessing air fuel sensor is also known as O2 sensor?

2.
dealership says a replacement sensor has been ordered but meanwhile I can drive the car safely. I'd have hoped they'd have provided a loaner before the sensor is replaced. Isn't it technically unlawful to drive (emission wise) with knowledge that O2 sensor is faulty? Also, with the VSC etc features turned off, it aint as safe as it should be with those features on - is that a good argument to haggle them for a free loaner?

Thanks. I'll attach a few pics on those funny dash "check engine" lights if I figure out how to download/send it from my new Moto V330 cell.

Very pissed it's giving me the trouble with < 15k miles.

 

[Northof49]

The most common cause of a CEL is a faulty oxygen or A/F sensor.....kinda the same thing, but newer vehicles use A/F sensors which are much more accurate. So yes, it's quite reasonable that a bad sensor is causing your CEL.

It's also ok to drive with a crapped out A/F sensor (provided that's the problem), the main problem would be slightly decreased fuel economy.

Plenty of vehicles don't have any VSC type systems, so I'm not sure how "unsafe" it is to drive around without them.....I'd rather drive a 4R with those systems disabled than drive a (presumably) lesser service vehicle, but others may feel different.

And no, it's not normal to have a bad A/F sensor at low mileage, but it does happen here and there.

 

[greasefingers]

O2 sensors are not the most reliable sensor in motor vehicles. Just think about the environment that they are in! The MAF sensor is located between the air filter and the intake manifold. It is one of the most important sensors on the vehicle. It is responsible for measuring the mass air flow rate (grams per minute), so that it appropriate amount of gas is injected to maintain approximately a 14:1 ratio. Without it the vehicle will not run or it will ignore the measured valve and use a pre-programmed curve built into the ECU?

The oxygen sensor will fine tune the air to fuel ratio, so it is not as important and the engine will run fine without it, a decrease in fuel mileage will be observed and emissions will increase. Many O2 sensors are replaced in new vehicles.

You are lucky that it was diagnosed and being replaced for free. For oxygen sensors, I think after 90 k miles; you are on your own?

 

[sharp4runr]

Don't feel too bad about it failing. Do a search and others have had similar issues. I had almost the same happen after I had the Sulfur TSB done.

Maybe there was just a bad batch of 02 sensors?

 

[tcpoob]

i picked up my runner last nite. asked about loaner and the guy reluntantly said they'd a Matrix. i didn't want to just leave my ride behind at the dealer's parking lot waiting days for the a/f sensor. drove my own ride home instead. like north49 said, it's still probably safer than a Matrix - that said, i'd haveloved to test drive that little car which i'd never driven.

the lights that stay on along with "check engine" are exactly as described in this thread
http://www.toyota-4runner.org/showthread.php?s=&threadid=4164&highlight=air+fuel+sensor

"vsc trac" and "trac off" are pretty confusing though if u think about it. does that mean both vsc and atrac are off - that's too bad.

14:1 ratio? i guess you are referring to a diff ration from the engine compression ratio - which is 10:1 on V6 and less on 4th gen V8s, iirc.

my crappy '97 (sold jan 05) had a faulty o2 sensor at about 60k which was replaced and covered by a "extended warranty" i bought. i paid probably $50 deductible. that thing costed a few hundred if i am not mistaken.

are people saying the runner has both a MAF sensor AND an O2 sensor?

 

[greasefingers]

For complete combustion the air to fuel ratio is 14.7 to 1 or 14.7 lbs of air to one pound of gasoline. Anything less than that is running rich and anything greater than 14.7:1 is running lean.

 

[boston_kevin]

I have a 2004 V6 4Runner and have had 2 Oxygen sensors replaced. Yea, it's very frustrating, and with all the snow we just had up here, once the VSC/TRAC is disabled it is very easy to spin the back end in 2WD. I really didn't notice any decrease in gas mileage since there are 4 oxygen sensors on the truck (1 on each side of each catalytic converter). My dealer said they had a bunch of these come in, all late model year 2004, and mostly V6... I only have 15k miles on mine too...

 

[tcpoob]

P0171 code

they said the sensor part is in so i dropped off the truck again at the dealer.

asked for the trouble code reported by check engine. said it's P0171.