I had pacesetter headers installed a few weeks ago and now both O2 sensors that are in the headers are throwing codes...

PO 134
PO 155

I will replace both sensors, but before I did I wanted to know if this was a common issue or if I should be investigating something else...

Maybe loose header bolts or something...

Also, pep boys and Auto zone seem to be confused when I ask them for the 02's I need...they only seem to focus on before or after cat, they have given me the wrong 02 and cant seem to understand that I want the 02's for the exhaust manifold...where else can I order from?

 

Ummm.... the only place that O2s are located is before and after the cat. Ask for the before cat one and youll get what your looking for, dont over complicate things. Did you replace your O2s when you put the headers on? You should replace them because during the headers first heat cycle they get very hot, hotter than normal post-break in operation. They could have got burnt up. That or its just a coincidence.

 

Thanks for the reply,

Let me give you a bit more info...On my car there are four sensors...

Drive side Exhaust Manifold
Passenger side Exhaust Manifold
Before Cat
After Cat

I asked for the before cat 02 from p-boys, but once I pulled the Drive Side Manifold sensor...the connector was not the same. The one before the cat is a female connector and the one at the exhaust manifold is a male connector...

But thanks for the other info you gave about replacing the sensors due to them possibly burning up... I did not replace them when I had the headers installed

 

Your car only has 3 sensors. The ones in the exhaust manifolds are considered the before cat sensors. If you have 4 that fourth one is some aftermarket thing. I put headers on my car myself and I can tell you absolutely for sure there are only 3 oxygen sensors. They could be giving you a universal oxygen sensor, the Bosch part number for the upstream O2 sensors on a 3.8, which I assume you have, is 13474. The manifold sensors have a female connector on the O2 sensor, and the car side is male. The after cat has a male O2 side, and female car side connector.

 

My car has four sensors. Two in the manifolds, one before, and one after the cat. At some point ('99 or so) they went to just 3 sensors as you described.

 

I love it when people say they are absolutely sure and they are wrong. My 96 has 4 O2 sensors.

 

I had a 97 Z that only had 3 sensors, one in each manifold and one after the cat(s). Gonna try and help or just say Im wrong? The part number for the O2 sensor with a male connector on it is 13444, they used the same downstream sensor since 95. Now, if your 3.8, still only assuming its a 3.8, is older than what Stang said, the Bosch number is 15703.

Sorry I didnt build the car gorn, I was looking these things up at work and our system only listed one downstream and two upstream, and that is all every car Ive ever seen had. Besides, how do you know Im wrong? He didnt give a year. Im not saying I was right, but neither of us know for sure, since he didnt give any info.

 

Bad information is worse then no information. You can really make a Newb look like a moron if he is out saying "someone added an O2 sensor to my car" And no he did not say what year or motor he had so by you saying "absolutely for sure" anyone reading it would assume you knew all the model and none of them had 4 O2 sensors. As for giving him the part number,,, well I hope where ever he buys it from he gets it by make, model and year cause if he gets it by your part number and its wrong its all his.

I am not saying don't help people just state "on my 2002 there is only 3 O2 sensor" so people know you are talking from a limited background.

 

Hey Guys thanks for the feed back...

My bad on not providing the year...its a 97 with the Y87 performance package...

Hope this helps

 

Usually, on OBDII cars (1996 & newer V type engines), the performance of each cat has to be monitored by federal edict. The number of O2 sensors depends on the number of cats. If two cats are installed, then four O2 sensors are installed, each bank will have an upstream O2, and each cat will have a downstream O2 sensor associated with it. (This is required by OBDII to keep track of the performance of ach cat). When a single cat is used, there still will be be two upstream sensors (1 per bank), and only one one downstream O2 sensor is used or needed.
The O2 sensors are available as either direct fit or universal. The universals have no connectors and the pigtails have to be spliced to the existing connector. The direct fit come with various types of connectors and you need to order the exact one.
The best way to test them is with a scanner and verify that the heater circuits are working and that the output voltage of the upstream sensors is always changing at a fast rate. The output voltage of the downstream sensors will vary at a slower rate if the cat is doing its job, or it will follow the changes of the upstream sensor if the cat is not doing its job.