Help with OBD II stuff

[Jessi]

Ok, I need a little help because I'm clueless.

Should I have an O2 sensor in the exhaust manifold and one after the cat?

I have a feeling I'm missing an O2 sensor.. the car is running rich and I'm failing emissions. I'm not saying that it's the only problem. But, one of the codes it's throwing out is a rear O2 sensor. I had a mechanic look at my car today and he said it looked like an O2 was missing.

If I do have one missing, Midas is going to hear an earful from me. :smash:

[S14DB]

You should have one in the mani and one under your ass.

[ALTRNTV]

Yes. There's one on the manifold and one right under your ass. Damn OBDII. The one under your ass will cost you.

[projectRDM]

The rear O2 is only used for diagnositcs, so even though it's missing that's not the cause of your car running rich.

[Jessi]

Thanks so much guys! I'm not paying for the one under the ass. :D

Midas' dumbass will be paying for it since they didn't put one back in after doing my exhaust.

R240NA, if there is one missing though, won't it cause like the pressure/air or something like that to leak out of an area it's not suppose to? I'm also getting the evap canister and vent control codes too. We're assuming with an O2 missing, it could be throwing both those codes as well. The mechanic said that the car shouldn't be throwing both those codes at once.

I am just so confused.. because I don't know what to do. I'm not good at explaining these kinds of things.

[S14DB]

I've only replaced the front one and run fine. But, every once and a while I'll throw the rear code and the ecu will start dumping fuel. It doesn't do anything but can still freak out the ECU if not there.

[Jessi]

Yeah, I have the following codes right now, and I'm assuming the O2 sensor is causing them.

1. Speedometer Head (not emissions related and nothing is wrong with it, but the check engine light never goes off, so we're assuming that's why this code is there)
2. Rear O2 sensor (not even on the car)
3. Evap canister
4. Vent control valve

[S14DB]

1. IIRC is the VSS. I would have to check the big black book at home.
2. Is the 02
3&4. Is that shit in your rear pass. fender behind the wheel. Been hit in that quarter? rip that shit out?

[Jessi]

I've never been hit on the passenger quarter panel. Just the drivers side.. twice!! This is all such a freaking headache. Give me your car. Haha.

[projectRDM]

R240NA, if there is one missing though, won't it cause like the pressure/air or something like that to leak out of an area it's not suppose to? I'm also getting the evap canister and vent control codes too. We're assuming with an O2 missing, it could be throwing both those codes as well. The mechanic said that the car shouldn't be throwing both those codes at once.

I am just so confused.. because I don't know what to do. I'm not good at explaining these kinds of things.

You'll have an exhaust leak, but I'm pretty sure you'd hear it. More likely it's just unplugged, either way it's not affecting anything else because you've already expelled what you need through the converter. You could cut the exhaust off right where it the sensor resides and the only downside would be volume.
The other two are likely caused by something else, I've seen cars with both of those codes and there wasn't any reasoning other than bad gas, age, wear, etc.

[Jessi]

Yeah, but my exhaust was custom made. And they didn't make an O2 sensor bung. I just now found this out yesterday when I took it to a real mechanic who actually took the time to look at the car.