2nd bank O2 sensor replacement

[pottsy710]

i was perusing the tips and maintenance subforum and didn't come across a thread there, if there is one i apologize in advance for posting here.

97 gp gt, 98k miles. anyway, i'm getting an error from the 2nd bank O2 sensor, i purchased a new sensor and plan on doing it this weekend, i know it's behind the cat, but i'm not sure if it's above or below the pipe.

any advice would be greatly appreciated!

[GPFred]

Since that's the one after the CAT, I would have the CAT checked. It could be the CAT is going bad and the O2 sensor is telling you based on the gases it is detecting. If its the O2 sensor, I would assume it is on the top of the pipe protected from road debris, etc. Good Luck.

[richtazz]

The sensor is in the u-bend part of the exhaust pipe just behind the converter. It points straight up toward the floorboard.

If you have your trouble code, post it before installing the sensor to be sure you need one. Your car only has 2 O2 sensors, one pre-cat and one post-cat, so there should be no Bank-2 anything listed, (although a generic scan tool may show them as Bank1/Sensor1 [pre-cat] and Bank1/Sensor2 [post-cat]). As GPFred said, many OBD-II codes don't necessarily indicate a problem with the related sensor, only that the reading from the sensor is out of range. Also, avoid Bosch branded oxygen sensors, they are highly unreliable.

[pottsy710]

i had my service engine light come on and had it read at auto zone, the guy said it was my O2 sensor in the "second bank", i got the sensor from morad for $20 so i figured it was worth a shot since i was getting something else from them anyway and it wouldn't cost any extra to ship the sensor with it.

is there another way to tell if it's the cat instead of the sensor?

and unfortunately i don't remember the specific error code that it was, is there a way to tell without a reader or should i run back up to autozone and then post what it said here?

[CrazyHorst]

The "u-bend" you are referring to is called the VOS-tube in some circles. This is for Vertical Oxygen Sensor.

The W-car downpipe is different from the C-H-G-car downpipes which have a horizontal O2 sensor and have a protection shield welded to the side of the post-cat outlet tube.

I think a supplier came up with this as a cost savings...hydroform the tube as opposed to source a stamping and weld it to the exterior of the tube. The W-car has the right underbody for this and the CHG won't work. It is constant-cross-section all the way thru so there is no restriction even though it looks like it.

FWIW GM Powertrain is responsible for the downpipe as they are responsible for the emissions performance (cat converter), the platform design groups are responsible for the cat-back exhaust.

[BNaylor]

Originally Posted by pottsy710

is there another way to tell if it's the cat instead of the sensor?

and unfortunately i don't remember the specific error code that it was, is there a way to tell without a reader or should i run back up to autozone and then post what it said here?

Go back to AZ and get the code otherwise you are just speculating because it may not be the 02 sensor but a CAT converter efficiency issue which would be a P0420 DTC.

[spddmn1]

Just got back from driving 477 miles from Kingsport, Tenn. back to Cleveland, Ohio today. My light came on & i have one of those scanners. Got a P137 code.

[BNaylor]

Originally Posted by spddmn1

Just got back from driving 477 miles from Kingsport, Tenn. back to Cleveland, Ohio today. My light came on & i have one of those scanners. Got a P137 code.

This is an issue with the post CAT converter 02 sensor. The 02 sensor or circuit related to it is shorted to low and in a lean condition. You can check the PCM 5 volt reference signal input to the sensor at the electrical connector and see if the output varies. Voltage output is in millivolts but greater than 0.00 mV.