I have a 1999 Dakota Sport 6cyl. with 116,000 miles. The check engine light started coming on the other day so I went to the parts store. The computer diagnosis said it was an o2 sensor. They only had the upstream in stock and said they could order the downstream. I purchased the one they had (upstream) for 50 bucks. He said they recommend I change the other too (another 50 bucks). Is this good advice or are they just trying to get me to buy both? Any advice would be appreciated. Thanks.

 

I will move this to the 2nd Generation Dakota sub-forum.

 

Yes do both. O2 sensors don't work as well when they get older and they cycle slower (duty cycle), giving slower info to the ECM.

The code might have only been thrown by one of them, but if they are original and have 116K on them, it's a good idea to do both.

 

well is better to do both