Bad o2 sensor = less power?

[zsiya]

I have a '99 Yukon with 209,000 miles. Recently, it has felt like it is down on power. The other day, the SES light came on indicating an o2 sensor (can't remember which bank). Would this bad sensor explain the lack of power?

 

[rockenthebowtie]

Most likely the 02 sensor isn't the cause for the loss of power but probably can give you a direction on where to start only the DTC will be needed there are multiple 02 sensor DTCs so need to know the exact DTC

 

[lesterl]

Get us that DTC P0XXX number.

What kind of mileage/ driving you getting/doing?

 

[2000tahoez71]

I was getting a PO420 code, insufficient catalyst. Going to replace the cats with the magnaflows next weekend and replace all four 02 sensors. I have read that one should replace all four with these motors instead of one due to the computer essentially comparing values of all four (at least comparing pre bank 1 to post bank 1, etc.). Don't know the truth but it sounds right. Little over a hundred bucks for all 4 (ACDelco) seemed worth it to me. At 209,000 you could probably use new ones.

 

[lesterl]

Where are you getting 4 acdelco sensors for little over a hundred bucks, they are like at least $60 each, the pre cat ones are a flat 4 pin plug, the post cat sensors have a square 4 pin plug....

P0420 is Catalyst System Efficiency Below Threshold Bank 1, possible bad cat.
What caused it to go bad? Fix that first.

I wouldnt just replace all 4 O2 sensors as the post sensors dont make adjustments to the fuel trims. Replace only if bad...

 

[2000tahoez71]

Amazon. One was 25 a piece the other 35 a piece. And I'm not sure about the cat. I had an exhaust leak that could have caused a rich condition and burned them up, but was also eating coolant and she had a rough life before she got to me so replacing them anyway.

 

[lesterl]

Burning coolant will take them out AFAIK....