99 Ls400 Oxygen Sensor Questions

[billydpowell]

the man just told you how to do it....... SO?

go ahead, jump under it, cut the wires, do it the "easy" way...

easy billy, put the flesh down and follow the spirit....

... good luck....

[Sanpete]

That was the question, whether that would be an easy way or not. May be harder for all I know. But thanks for your advice.

[Micah.Berry]

Ha! Thanks, Billy.

Sanpete, you can splice the wires and use a generic O2 sensor if you would like. That would keep you from having to pull the carpeting up. It's a bit of a pain to pull the carpeting by the gas pedal. The reason that I would recommend a Denso (OEM) plug is because you'll know that it works; there is no splicing - eliminating any errors due to poor splice jobs. In addition, from a cost perspective, the plug and play Denso plug wasn't that much more expensive than a off-brand, splice style sensor. One you get the carpet up, it's literally plug and play versus trying to splice wires in tight confines above the cat (it's really tight there).

You'll need to make your own assessment as to which way you want to go based on how much you want to spend, and whether you want to pull the carpet on the transmission tunnel there by the gas pedal. If it were me, I would pull the carpet.

This was my experience with the O2 sensors: In my research, I was getting a P0420 code for a non-functioning cat. However, the shop that I took my 99 LS to stated that they didn't think it was the cat. They thought it was the downstream O2 sensor. While I did a lot of research understanding how to replace the upstream and downstream O2 sensors, I wasn't quite satisfied with that answer. My gut feel was that it wasn't right. Temperature readings before and after the cat fell within expected values, indicating the cat was functioning properly. And the O2 sensors will throw off their own codes when they fail, if I understood correctly what I read. Further research revealed the gasket between the cat and the pipe was prone to cracking and allowing exhaust to escape, and subsequently causing the computer to think the cat wasn't functioning at proper specs. I got underneath the car (again) this time to carefully feel around the cat, and sure enough, there was a little crack that had a puff of exhaust coming out. I sealed it with some high temperature gasket maker, intending to properly get it fixed a little later. Pushing two years later, I've not gotten any more codes.

[Sanpete]

Thanks again, Micah. If it's tight from under the car, it's probably not that easy to splice in the universal and do it well, as you say. Denso does offer the same sensor in universal form, but the one with the connector is fairly cheap now, $42 with shipping at Amazon (Denso 234-4169).

I came across some stories like yours about the gasket causing fault codes. One guy finally replaced his and saved a bunch compared to what the shop wanted for replacing the cat. With about 165K miles, this is the first code I've had since I got the car with 141K. Hopefully the gasket and other sensors will hold on a while longer. The only other thing I've had to do was replace an o-ring on the power steering pump--happily only one, the one that can be gotten to easily, was leaking. I'm so happy it wasn't the high-pressure hose. So far so good.