Is O2 sensor gone bad??????

S70 Guy · Post by **S70 Guy** » 27 Nov 2005, 20:52

I have a 98 S70 GLT. How do you tell if an O2 Sensor is gone bad. I read in a post for the 740's that you just unplug it and see if it runs different. If it doesnt then its bad. If it runs noticebly different then its working.
Any truths to this process? Or better ways to tell if its working properly?

Thanks

Post by **matthew1** » 27 Nov 2005, 21:01

Check Engine light and/or gradual economy slide, down to 15mpg or worse.

Guest · Post by **Guest** » 01 Dec 2005, 14:40

I thought I read around here about the MAF also being a possible cause of poor gas mileage. There was a thread somewhere, here I think, that said if it is in decent shape, you can tap on the MAF and it will behave normally for a while and gas economy will improve/return to normal but that eventually mpg will decline again. Of course, you can replace it, apparently even with one that is made for other than Volvo models (=cheaper part cost). *Someone please confirm, the memory is going...*