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March 23, 2012

Replacing Oxygen Sensors in a 1999 Honda Civic

expired oxygen sensor

expired oxygen sensor

Recently the “Check Engine” light came on in a vehicle sometimes known as  “Gimli’s Beach Chariot” , actually my wife’s 1999 Honda Civic. The car has about 200,000km on it (and not much rust, being a BC vehicle.) An OBDC II code reader showed the problem code as Power Train 0141, related to the lower oxygen sensor. This turned out to be a pretty simple repair (nice when that happens). The hardest part, no surprise, was getting the old corroded parts out. Here’s what I did.

First, it’s helpful but not essential for this repair to have either a service manual or Haynes manual to help in locating parts around the engine:



Note that if you buy a manual by clicking on the appropriate image, I get a small commission. Even better, if you really want to help support a starving author, you can buy my new book Dog Friends. Our dog Gimli rides to the beach in a ’99 Civic :-). Click on the book image for details and previews. And please look out for my forthcoming book about repair!

The two oxygen sensors of concern, upper and lower, are located respectively above and below the catalytic converter, which is bolted in front of the engine. That’s great for home repair purposes, since there is no need to even lift the vehicle. In fact, there aren’t too many parts in this car more accessible than the O2 sensors. A few months back, I’d had to replace the upper oxygen sensor in the same vehicle. In that case, the problem had produced OBDC code 0135. Resistance measurements on the sensor showed it to be an open circuit, instead of the expected <100 ohms. In that case, the sensor was easy to get at with a wrench, and with some torque applied, it was not too difficult to remove. Here you can see the replaced upper sensor on the engine:

upper oxygen sensor

upper oxygen sensor

The lower sensor turned out to be just slightly more work to get at. I didn’t have the specialized sensor wrench that would have made it easy to get at the sensor nut collar, but I found it fairly easy to remove the 10mm -head bolts holding the lower cat heat shield onto the catalytic converter. The heat shield then came off easily and I could get a standard box wrench on the sensor collar. I would have preferred to have the correct, specialized tool for the job (a subject for another post), but I had a rare sunny afternoon in Vancouver to do this job and so I just used what I had on hand. Before you do the bolt untorquing work, you’ll want to first disconnect the wiring harness connector for the sensor, and removing the sensor-side connector from its bracket that holds it to the car. There are 2 press tabs, one for holding the mating connectors togethor, and one for releasing the connector from the bracket; just depress each tab gently and pull apart.
sensor connector closeup

sensor connector closeup

lower shield and O2 sensor area

lower heat shield and O2 sensor area

Once I got those and the shield off, I found I could easily get a regular box wrench onto the old sensor and torque it out. It was a bit stiff to break the threads loose, but after that, I could turn it the rest of the way out with fingers (OK, I am a rock climber, but seriously, this was easy). I replaced the failed sensor with a Bosch model 13249 sensor from Autopartsway Have used them for sourcing many other parts previously, no problems.
I also found that the wiring on the new sensor left more slack in front of the engine than I thought was safe, and there was some chance of the wiring insulation contacting hot exhaust parts, so I used a pair of nylon straps to secure a rubber surround on it to a secure spot on the car in front of the engine, as you can see at the bottom of the picture above, still leaving some slack for slight relative motion of those parts.
After tightening the new sensor into place (a handheld mirror helps to inspect from below), and putting the heat shield and its bolts back in, I cleared the engine codes with my reader and cranked up the engine. Success: no more ‘Check Engine’ light and the engine seems to be running fine.
For the record, the one “specialized” tool I used for this repair was an OBDC II code reader that I got more than a decade ago from Canadian Tire that has served me well several times over the years. This was used for reading the trouble code and then clearing it after the repair. There are many online sources for trouble code lookup too. There are newer, improved models of these OBDC readers on the market now but the one I have did the job. Welcome to borrow mine if you are near me in Vancouver, though; I like to encourage tool sharing (a subject within the book that I am writing these days).

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