o2 sensors.....how to tell if they are bad?

I doubt you have two going bad at the same time. I would keep looking for that vacuum leak. You could also switch the rear o2's to the front just to be sure, but I am betting that there is a leak letting some unmetered air into the engine somewhere.

if you really want to go nuts, back probe the white and black wires and take an Ohm reading with a multimeter and see if it fluctuated at all. thats how i trouble shot mine when i nitroused them to death

ImportEater98 said:

if you really want to go nuts, back probe the white and black wires and take an Ohm reading with a multimeter and see if it fluctuated at all. thats how i trouble shot mine when i nitroused them to death

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you can also use an a/f guage, which if you don't have a wideband, is about all they are good for. I had mine hooked up to a switch so I could switch between the left and right o2, so I could see if one was drastically different than the other.

ChadS98GT said:

I just put a PI intake on my car and I have thrown a few codes.....

this all started with what I thought might be a leak....heard a whistle at idle from the engine...couldn't pinpoint it...but it was gone the next morning....and now I am left with this...

P0174 System Too Lean - Bank No. 2. Bank 1 also....

some of my buddies are saying that it could be my 02 sensors....
is there any easy way to tell if they are bad?? I really don't want to spend a c note on some sensors that arn't bad....


What could cause them to suddenly go bad?

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All the rear o2 does is measure the efficiency of the cat. The front o2 is the one that controls lean/rich commands sent to the computer. It sounds likely that you have a vacuum leak (unmetered air source) combined with the added feature of having too much air from your new intake. The best way to test the O2 after seeing the machine on a 4 gas machine, is to put it on a labscope and watch the pattern and see that it is occillating rich and lean equally with 450mv as the center line. Assuming that you don't have a labscope, you can use a multimeter after backprobing it with a sharp T-pin (making sure not to damage the wiring in the process) to watch the voltage go up and down. Now, understand that the sensor moves up and down at a rate of like every 10ms. that's pretty fast. If it's going up and down so fast you really can't keep up it's good. If it stays mostly around 450mv and occillates slowy or not all you can bet it's bad. That would be what's called a lazy O2 sensor. To eliminate the injectors, you can do what's called a noid light test. If you have a set or can buys or borrow a noid light set from someone, you can hooke them up to the injector harness to see if the injectors are recieving a good signal to the injectors. BUT, like has been said earlier after your O2 test, start looking for a Vac. leak, and see if you can get an A/F guage hooked up to watch what's going on.