AspektVIP

Hey guys I’m new to working on cars and I have to replace a knock sensor on my 99 ls400. Where can I find how to do this step by step preferably. Also where should I buy it from

peterls

I haven't done it, but the job is pretty much the same as replacing the starter, without actually replacing the starter - knock sensors are in the same place. If you are going to go that deep into the engine, and if your starter is old, you may as well replace the starter too. BTW, do you have new knock sensor harness? Being in the hot place they are, the harness goes bad over time and should be replaced too, but it is a hard item to find these days. For 1st gen, pretty much impossible to find new.
I think that that's the hardest job to do on our cars, so I took mine to a shop - let someone else bust their knuckles on that one.

deanshark

I wouldn't suggest this job if you're "new to working on cars". I agree with peterls about changing the starter and knock sensor harness while it's already apart. It's one of the hardest jobs on these cars. (except heater core ) Check around to see what you can get for a price from an independent repair shop, one that specializes in Lexus would be good.
If you do try to tackle it there are some good threads in here about changing the starter. That's what ya need.

AspektVIP

Ive already replaced the starter, i heard that denso knock sensor is the way to go but i cant find where to buy them.

peterls

If you are looking for original, OEM, Lexus knock sensor, the manufacturer seems to be Hino (or Toyota?).
For gen 1, part #89615-50010
for gen 2, part #89615-12040
You can find OEM on amayama for about hundred bucks, or try your luck on e-bay. I bought mine on ebay, and if I remember correctly, I used Denso too. Same sensors are used on other toyota vehicles, so we'd probably hear by now if they (Denso) were no good. I replaced mine 5 years ago, and no problems at all.
If you are replacing knock sensors, you probably want to replace the harness that plugs into them as well.
BTW, I heard that there are a lot of knock-offs being made in China and sold as OEM-Denso Knock sensors. Don't know if it is true, but I do find it strange that e-bay has million of listings for the OEM, Denso knock sensor for ls400 at $15.- or so, when OEM costs more like $150-200. Also, when you buy Denso, as aftermarket it willl NOT come in a Lexus part bag marked with the part number and all - and these all do. So I am suspicious of them as all heck. Buyer beware.
I remember paying around $50 ea. for mine. How did the price drop so much suddenly? Hmm...