How do you replace an O2 sensor on a 1998 Toyota Tacoma?

Answer 1

Crawl under the truck up under the passengers side door and look for the catalyst converter (in line with the exhaust pipe). You should see this after crawling in a foot or so. There is a sensor before and after the catalyst converter. The oxygen sensors are those things you'll see sticking out with wires attached. They are held on by 2 nuts (10mm). I'd recommend spraying the studs/nuts with some sort of liquid wrench or PB Blaster and let 'em soak awhile before trying to get them off. Once it's soaked awhile just take off the nuts and the sensor will come right out. There is also a wiring harness that's about a foot or so long that contains 4 wires the needs unplugged. On one side of the plug you should see a plastic lever to push in on while pulling the connector apart. The Toyota part numbers for the Front sensor (closest to engine) is 465-39885 and the rear sensor is 465-39785. Also it'd be a good idea to replace the 2 gaskets, part # 466-20020. (Flange nuts are 10 mm 8 by 1.25 pitch in case you need to replace those) I'd also recommend replacing both sensors if they are about the same age. Apparently the common thing to fail in these units is the heater which is built into the sensor. I have prolong the life of a few sensors by soaking them in a shot glass full of throttle body cleaner (make sure it's safe for O2 sensors) over night, stirring occasionally. These sensors aren't cheap so if you are on a budget, it's worth a try. To clear the "Check Engine Light" code, pop the hood and open up the top on the fuse box on the drivers side and look for the fuse that has "EFI" on it (bottom left corner I think). Take the fuse out for a minute or so and then replace. This will reset the ECU and you'll have to drive it 50 miles or so for it to learn your driving habits again so don't be alarmed if it runs a little rough those first 50 miles or so. Driving the truck up on ramps or lifting with a floor jack (and supports) would make things much easier, but when I did mine I didn't have anything available at the time. Happy Trails ........ Jack :-)