Cannot locate Oxygen Sensor on 1999 S10

I am attempting my first tune up using a Haynes manual and the internet for direction. The run down of things to do includes replacement of the oxygen sensor but I cannot find it. In fact I don’t see it anywhere in my Haynes manual either. I find plenty of them for sale for a 1999 Chevy S-10 4cyl, so I’m guessing it exists, but where is it?

Follow the exhaust. There’s either one or two. First place I’d check is the exhaust manifold. Follow the exhaust down to the catalytic converter. There should also be one AFTER the cat too.

BTW…Why are you replacing the O2 Sensor??? Is it giving you a code??

I watched a “how to” video on tune ups and it told me to replace the plugs, plug wires, pcv valve, and o2 sensor. The truck has 88K miles on it. No codes. It runs just fine. I thought I would just change it preventatively. I know nothing about cars but I have learned my way around a motorcycle. It seemed that since I could fix my motorcycle, I should learn to work on my truck too.

If the trucks mileage and performance are OK after changing the spark plugs, wires, pcv valve, air filter, fuel filter, I would leave the O2 sensors in place.

Ditto to all of the excellent advice above.

The one and only reason that I changed the O-2 sensor on my 87 Ranger is that it had 180,000 miles on it.

I thought replacing it might make a difference in performance & MPG. Wrong, it made no difference whatsoever.

Lesson learned is if the computer is happy with the O-2 and not setting an O-2 code, just leave it alone.

I agree. The O? sensor is monitored by the computer and it will tell you if it needs replaced. The method used to monitor plugs and wires is not a efficient so you should just replace them on the schedule. I don’t believe O? sensors are included on the items that should regularly be replaced as listed in the owner’s manual. That is the Bible for those things.

I’m glad I asked. Thanks all!

  • Mark.

I concur…There is no need what-so-ever to replace the O2 sensor if it’s not giving you a problem. I’ve had to replace ONE O2 sensor on the last 4 vehicles we’ve owned…And that was around 270k miles. All the other vehicles reached OVER 300k miles with the origional O2 sensor(s)