O2 Sensor question

Hello,
I'm new here, so I'm not sure if this question has been asked before. I bought a 1999 Tahoe last year, and have since replaced a catalytic converter (I can't remember which one. I'll have to check the receipt) because of the rattling noise that it was making, as well as the check engine light.

Since I've had it replaced, I don't have the same noise, but I'm still getting the check engine light, as well as a different noise while I'm riding along. It's a rettling noise as well, but different from the noise of the catalytic converter. When I used the code reader, it gave me a message that hints to the O2 sensore bank 2.

I need to know if this is the sensor before or after the catalytic converter, and if this would be a job for someone with limited mechanical knowledge.

Thanks

Code will tell you before and after cat and bank 1 vs 2.

I think driver side is bank 1 but you should verify.

Code will tell you before and after cat and bank 1 vs 2.

I think driver side is bank 1 but you should verify.

Bank 1 is the side where cylinder 1 is (drivers side).
Bank 2 is the side where cylinder 2 is (passenger side).

Sensor 1 is 1st sensor on a side. Sensor 2 is 2nd sensor on a side. Sensor 3 is the 3rd on a side, etc.

Therefore, if there are 2 cats each with a pre and post 02 sensor, Bank 2 Sensor 1 would be the pre cat 02 sensor on the passenger side.

//2000CAYukon

Thanks alot

After I read your comments, I went out to re-read the codes, just so I'm giving the right information. The results are as follows:

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
O2 Sensor CKT No Activity (Bank 2 Sensor 1)
O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
O2 Sensor Sensor CKT Slow Response (Bank 2 Sensor 1)

It seems to me that I'm basically dealing with 2 sensors ( one in bank 1, and one in bank 2). If bank 2 is the passenger side, then that's the side where the catalytic converter was replaced.

So, now I have 2 more questions just for clarification.

1. If "Bank 2 Sensor 1" means the first sensor on the passenger side, is that before or after the catalytic converter?

2. I know that having malfunction codes are bad, but is the issue with the "Bank 1 Sensor 2" as serious as the "Bank 2 Sensor 1", since it only gave one code?

Thanks so much for your help!!

Can you post the code no and what engine.
But remember code only say check it out not that the sensor is bad or replace the sensor.
The sensor circuit or wiring can give a lot of problems and engine running rich or lean can set 02 sensor codes to.
Proper testing is the key to any codes.
MT

I had a similiar problem (no Heater circuit) on 1997 Tahoe with 140K miles on bank 2 sensor 2.

I disconnected the sensor and reconnected, reset code, and did not come back. I assume bad connection. I plan to clean with contact cleaner & put some silicon grease (used for spark plugs) on it.

No heater will cause slow response so this is where I would focus.

As I recall 12V (battery) is applied to all 4 the heaters from the EMU without separate fuse and the low side of the heat goes back individually to the EMU to monitor current draw of each. When the current draw is out of warm-up profile a code is thrown.

I would focus on the connections at the two sensors. They may have been removed to replace the cat and not fully closed. They need to be fully installed so the clip on connector latches (use small screw driver to lift when removing).

From my research I doubt the heater elements in O2 sensors are bad. But these sensors have a general life of 100K miles. I would try to fix heater problem first but if sensors are old they will need to replaced to avoid other / future problems.

You could measure the 12V and resistance of heater but it's a pain without wiring from an old o2 senor. There is a full procedure in the GM Shop Manual for this requiring this jig. I find mine at library.