View Full Version : Need help with O2 sensor.

05-02-05, 03:53 PM
I have a 1996 Deville, and I need to replace the front Oxygen Sensor on the driver's side. I can't find it to replace it. Does anyone know where it is located?:confused:

05-02-05, 04:22 PM
There's not one "on the driver's side," really. There are 4 sensors. They are numbered and located as follows:

Bank 1, Sensor 1: In the exhaust manifold for the rear cylinder bank
Bank 1, Sensor 2: After the Y pipe before the catalytic converter
Bank 1, Sensor 3: After the catalytic converter
Bank 2, Sensor 1: In the exhaust manifold for the front cylinder bank

If I remember right, the B2S1 sensor is kind of on the driver's side where the B1S1 sensor is more on the passenger side, but that might not be right. If you locate the manifold, you can't miss the sensor. It sticks out at a right angle and has a wire harness connected to it. It takes an O2 sensor socket to remove and install.

Post the code or the BxSy numbers and we can tell you exactly what to do. Do you have a new sensor already or do you need one?

05-02-05, 05:10 PM
I have a '97 DeVille, and the one I had to replace was, of course, the hardest one to get to...the rear exhaust manifold. What a bear!! *lol* I don't recall what my DTC was at the time. It cost about $70 for a Bosch replacement.

05-02-05, 08:33 PM
I baught an O2 sensor from Autozone. My son can't see where it goes. My Son can't find the exhaust manifold from under the car, do we need to get to it from above?

Thank you for your response.

05-02-05, 10:16 PM
It depends - which 02 sensor are you talking about? As mcowden said, there are four. Three of them are easy to get to. But the one on the rear exhaust manifold (B1S1) is a nightmare. I believe that all the 02 sensors are different, with different part #s, so it matters which one you order and subsequently replace.

I suppose that someone probably makes a special socket for changing that one from above. I would check and see first. Even so, you will have to unbolt the coil pack on the rear valve cover and lay it aside to gain access to the sensor. If not, you may have to pull the exhaust Y pipe from underneath to get at it. That's how I changed mine. (I'm too cheap to buy any more tools! *lol*) Be sure to disconnect the battery's NEGATIVE cable before attempting any repairs.

05-02-05, 10:26 PM
I believe there IS a special O2 sensor socket.

05-06-05, 11:15 PM
NO, NO, NO. the O2 sensors are not all that hard to do. The one on the back of the engine or Bank 2 is very easy to see. But you will need the tool --- AutoZone rents the unit for nothing ie. you buy it then return it.

You will want to remove the cross brace running from one shock tower to the other. You do not need to remove the coil pack but it does help --- i did it without removing it. the tool looks like a crows foot that is the one to use not the one that looks like a socket it will not work for the bank 2 O2 sensor.

The front O2 is kind of hard to find but you must do this one from the bottom you wll need to remove the splash shield to get to it, it is slightly closer to the drives side but about in the center -- you will also need to remove the air cleaner box and the duct running from the box to the throttle body. You will need to remove this because you will need to get your hand down from the top to get to the O2 sensor's plug. One hand down from the right side of the radiator hose and the other from the left side of the hose. Cant do it with one hand. It is very tight.

Note: the plug has a key or lock that is pushed thrugh the connector to prevent the plug from comming off. this is the hardes part of the job -- getting that out --- so do it first. when it is unplugged then take the O2 sensor out. If i remember correctly you may not need the special tool on the bottom O2. But you will for the back one for sure. The O2's are not in very tight you will need to break them free with about a quarter turn then they are loose enough to do with your fingers.

Now: if you were getting an OBDII reading of PO171 or 174 that may not be the O2 Sensor it is prabably the MAF sensor. You can clean the MAF with electrical contact cleaner --- Just spray the crap out of it. Earler i recomended Carberator or break cleaner for this job but that is a bad idea use electric contac cleaner without a lub or grease in it.

Good Luck --- remember if you have to replace the O2's MAF,MAP, and TP it will still be cheeper than one Cadillac dealer service.

05-07-05, 07:31 PM
The O2 sensor for the rear cylinder bank is the Bank 1 sensor 1. Bank 2 is the frontmost sensor in the car, and it's the only bank 2 sensor. The B1S1 sensor can be accessed using the crow's foot and a good extension from above. I didn't touch my shock tower brace or the coils, but that's on my '96 SLS and may be different on other models.

There are 2 different O2 sensors for the car. The "rear" sensors are the ones before and after the catalytic converter. The "front" sensors are the ones on the manifold for each bank of cylinders. They are all heated O2 sensors. So, that is to say the B2S1 and B1S1 sensors use one part number, and the B1S2 and B1S3 sensors use another style.

Hopefully that clears up some of the confusion.

05-09-05, 08:39 PM
Thank you all for your help.:)