1999 Pontiac Bonneville V6 3.8L Upstream O2 Oxygen Sensor Walker Products 250-24018

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Hi, I'm Don from 1A Auto. I hope this how-to video helps you out, and the next time you need a part for your vehicle, think of 1AAuto.com. Thanks.

In this video, we're going to show you how to replace a downstream O2 sensor on this 2002 Chevy Suburban. We show you on the passenger's side, but the driver's side has a similar procedure. You'll need a new downstream O2 sensor from 1AAuto.com, a flat blade screwdriver, a 7/8"? wrench, and some wire cutters.

To start off, we're going to show you where your O2 sensors are. On this side, on the driver's side, it's the Bank 1, Sensor 1. This is Bank 1, Sensor 2. This is on the passenger side: Bank 2, Sensor 1 and Bank 2, Sensor 2. Both Sensor 1s are your upstream, and both Sensor 2s are your downstream. We're going to do Bank 2, Sensor 2, which is the passenger side downstream O2 sensor.

You just want to pry out this clip, pull the harness down, pull out that pin, then pry up the tab, and disconnect the harness. Use your wire cutters to cut off the harness connector at the bottom of your O2 sensor. We do this so we can get the closed end of the wrench onto the O2 sensor. Now slide your 7/8-inch wrench into place and using another wrench for leverage you want to pry it and break it free, and then twist it out the rest of the way. We'll fast-forward as Don does this.

Obviously, we have the vehicle up on a lift, but, actually, there's enough clearance on these vehicles that you don't even need to jack them up to do this. On the left is the old downstream O2 sensor; on the right is the new one from 1AAuto. You can see they're going to fit exactly the same.

Take your new downstream O2 sensor, feed it into place, and just twist it in. I'll fast-forward as Don does this and then tightens it up with the wrench. Now just reconnect your harness and then push that pin back into place. Then re-clip the harness to the vehicle. You're all set.

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Hi, I'm Mike from 1A Auto. We've been selling auto parts for over 30 years. We're dedicated to delivering quality auto parts, expert customer service, fast and free shipping, all backed by our 100% satisfaction guarantee. Visit us at 1AAuto.com, your trusted source for quality auto parts.

In this video I have a couple of oxygen sensors with me. While there are some aesthetic differences here, the wire lengths are a little different, the actual body and tip of the sensor are a little different, the threads and gasket are the same, and on the other end the connections are actually the same. I can plug these into either position on our vehicle. But if I had to ask you which one's upstream and which one's downstream, you probably can't tell just from looking at them. That's true of most oxygen sensors. The way you determine whether or not an O2 sensor is upstream or downstream is all done visually.

Your oxygen sensor position can be determined relative to your catalytic convertor. As the name suggests, upstream sensors will be located upstream or ahead of, in front of, above, closer to the engine than your catalytic convertors. This means that they see the exhaust gasses first. They then go through the catalytic convertor and to the downstream oxygen sensor, which will either be located in the catalytic convertor like our vehicle here, or after the catalytic convertor to monitor the gasses coming out of the cat and make sure that it's being efficient relative to the readings of the upstream O2 sensor.

The other determination you need to make is bank one versus bank two. Determining which bank is which can be done by looking at a picture of your vehicle's firing order. Whichever bank contains cylinder one is going to be bank one, and the other one, regardless of whether or not cylinder two is in it, is going to be bank two by default. These banks are true of V engines like V8s, V6s, and flat engines like Porsches and Subarus that have individual banks.

On inline four-cylinder engines, as long as they have one exhaust manifold like a Jeep four-liter or a four-cylinder Honda engine, you'll only have one bank with an upstream and downstream O2 sensor. There will be no bank two on the engine.

On our vehicle here, this is the passenger side, which we've already determined from the firing order is bank one. We have our upstream sensor here closest to the engine ahead of the cat. Then we have our downstream or sensor two here inside of the catalytic convertor. This could also be located somewhere after the cat. Here I have my two sensors for the vehicle. While they are aesthetically different, we can now tell this is my upstream sensor because it looks just like the upstream sensor I have up there. This is my downstream sensor. Now that we know which one's which, we can order the right part, correct the problem, and fix you up right.

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