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Replacement of Oxygen (O2) Sensor: 2.0L Jetta/Golf GTI/VW MKIV

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how-to-replace-a-02-oxygen-sensor-20l-jetta-golf-gti-vw-mkiv-diy-cheap

Oxygen (O2) Sensor DIY for VW 2.0 L Engines

Here is a way to take the cheap Bosch oxygen sensor #15718, made for Ford cars, and use it in your 2.0 Volkswagen engine. This is an old trick on the MKIII engine but has not been tried on MK4 Jetta, Golf, and GTI models. These sensors have been proven to work on BMW, VW, Saab, and a list of other cars: why not save money and use them on yours?

Recently, I picked up a 1999 MKIV Jetta 2. It was slow, and as good as the thing looked, it ran like sh*t. After replacing the downpipe and cat (this car failed emissions hard), I was getting error code 16518, "No Activity Bank 1 Sensor 1" on my VAG-COM. As well as 16521, "Bank 1 Sensor 2 Signal Intermittent," which I wasn't too concerned about.

After pulling out the first sensor and seeing the date of 1999, I knew this thing was rotten like an outhouse. So, like anyone else trying to save a buck in this economy, I went to the World Wide Web and found my solution: I just had to soak this bad boy in gas for a few days and it would run like new! Nope! Fail. Maybe it works for some, but it definitely did not work for me.

If you have read my other DIY's you know I'm all about saving money, and 02 sensors are not cheap. For a "narrowband" oxygen sensor—I have no idea what that means, so don't ask— the price ranges from $70-$200 depending what you buy and where you buy it from. Add on another $150 if you're having the dealership change it for you. Sorry, but even $70 is too much for me, for a sensor.

So once again, I come through with another cheap DIY for all you others that refuse to pay VW prices.

After hours on the World Wide Web, the cheapest option I could find was a universal 02 sensor for 67.99 at AutoZone. I also came across some posts for VW's, BMW's, and Mercs all stating that they were using cheap Ford oxygen sensors, and replacing the harness plug, like you would have to do with the universal 02 sensor anyway. I could not find any documentation on someone using this sensor on an MKIV, but others stated it works great on their MKIII, so for the greater good of mankind I gave it a go.

The sensor is Bosch part #15718, sold at Advance Auto for 47.99. 47.99!!!! That was way too much for my cheap a**!!!. I added in a can of Liquid Wrench to get it up to $50, and used a coupon code ("RETMENOT123") for $20 off. My total: $35.

Note: This cheap Bosch sensor will not work for you if you have a Jetta with a "wideband" front 02 sensor, which has 5 wires. At some point between 1995 and 2002 (I'm looking it up), Jetta began using wideband sensors. If you have one, begin your research by calling your VW dealership and see how much they would charge for a front sensor; some old ones may be on clearance.

Tools you will need to replace an O2 sensor in VW 2.0L engines.

Tools you will need to replace an O2 sensor in VW 2.0L engines.

Tools for the Job

Most of these tools are pretty common in a toolbox. The only ones that I would recommend buying are 1) the 02 sensor socket, part #95045 at Harbor Freight for $7.99 (use the 20% coupon and free flashlight coupon in the paper to get your money's worth) and 2) a wire stripper; sorry, no tips as where to get that cheap. If you don't want to use the 02 sensor socket, you can take off the heat shield, held on by five 6 mm Allen head bolts (and one 4 mm I believe), which will give you enough room to work an adjustable wrench down there.

  • Can of WD-40, PB Blaster, or Liquid Wrench
  • Adjustable wrench (at least 22mm) or socket wrench
  • 02 sensor socket (part #95045 at Harbor Freight)
  • Scissors
  • 10 mm wrench or deep socket
  • Anti-seize (small packet for a dollar)
  • Wire strippers
  • Butt connectors 18-22 gauge ($2.99 for 21 pieces at AutoZone) or heat-shrink connectors if you're a big spender (10 pieces for $5.99)
  • Vise grips
  • Electrical tape

Removing the Old Oxygen Sensor

The very first thing that needs to be done is spray all around that sensor with your WD-40, Liquid Wrench, or whatever. If you're not sure where the primary sensor is, look at the first picture below, go to your car and look between the firewall and intake manifold, and you will see it; the wires stick up like a cute little puppy tail on the back of the heat shield.

What are you doing? Why are you still reading? There is plenty of time to read. Now go out there and spray down the sensor so you will be able to get it off.

how-to-replace-a-02-oxygen-sensor-20l-jetta-golf-gti-vw-mkiv-diy-cheap

Hopefully you have your car jacked up or on ramps, or you're skinnier than Ashley Olsen on a coke diet, cause it's time to wiggle yourself under the car.

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On the passenger side, about a foot away from the cat, there is a black box with wires going into it (see picture). The box is held on by two plastic 10 mm nuts, so this is where your 10 mm deep socket or wrench becomes a handy tool. Remove the nuts and pull the box down.

how-to-replace-a-02-oxygen-sensor-20l-jetta-golf-gti-vw-mkiv-diy-cheap
how-to-replace-a-02-oxygen-sensor-20l-jetta-golf-gti-vw-mkiv-diy-cheap

Once the box is down, as you can see in the pictures, there is a little plastic wall that holds the harnesses in place. The brown harness is for the post (back) 02 sensor and the black is for the primary (front) 02 sensor. Pull the black harness out of the wall and unclip it. Once it is unclipped release the wires from the clips along the bottom.

If you go back to the top of your car, you should be able to pull the wires and harness up into the engine bay; if not, get back under there because you missed a clip.

how-to-replace-a-02-oxygen-sensor-20l-jetta-golf-gti-vw-mkiv-diy-cheap

By now, hopefully, that WD-40 or whatever you use has soaked the grim years off of your oxygen sensor and you can unscrew it. You can slide your 02 sensor socket on and either use an adjustable wrench on the top or a 3/8th socket wrench to unscrew it. You can also remove the heat shield if you want more room or you just want to pull it off with your adjustable wrench. With the heat shield off ,I could get the sensor out easy; with the heat shield on, the only way I could get it out was with the 02 sensor socket.

Splicing the Wires and Installing the O2 Sensor

The Ford sensor #15718 only has about 15-16" of wire. You're going to need around 30", so don't get too eager and cut off your VW harness just yet, lthough you can cut off the plug of your new Ford sensor as close as you can towards the connection.

From the harness, I would measure about 16-20" of wiring on your original sensor and cut it off there. Using your wire strippers, take about a little less than a centimeter off of your harness wires and your new 02 sensor wire.

Time to crimp it all together! With the Ford plug all the wire colors match correctly, and the heating wires have no polarity so it does not matter how you connect those. White to white, black to black, and gray to gray. I used vise grips to crimp them and standard butt connectors like I listed above, but if you're baller status and care about the car you're working on, use the heat-shrink connectors and a wire crimp tool.

how-to-replace-a-02-oxygen-sensor-20l-jetta-golf-gti-vw-mkiv-diy-cheap
how-to-replace-a-02-oxygen-sensor-20l-jetta-golf-gti-vw-mkiv-diy-cheap

Maybe it's going overboard, but to be safe I took two pieces of the wire heat shield from my old sensor cut it to size and sliced it down the middle with my scissors, then wrapped it with electrical tape to keep the water out.

how-to-replace-a-02-oxygen-sensor-20l-jetta-golf-gti-vw-mkiv-diy-cheap
how-to-replace-a-02-oxygen-sensor-20l-jetta-golf-gti-vw-mkiv-diy-cheap

Re-Installation

Re-install in reverse of the way you took everything out, but make sure you cover the threads of your sensor with anti-seize, or have a fun time trying to remove it again.

No Problem Running Bosch 15718 in VW 2.0L

I have had no problem running this sensor at all in my MKIV. I did try the same mod using a Denso sensor for a Toyota as the post sensor, and it did not turn out as well, which from what I've read has to do with the ohms.

I write this stuff to help; if you f*** up your car, that is your problem, so don't complain to me. Comments are always welcomed.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

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