bdazzler

Yes, there should've been a washer included. SHM at Toyota. If you go to Page 1 on this thread look for Zoraone's reply, there's a photo of one he bought from Autozone I think he said. You might be okay without it, look to see if it leaks or not...

RE the ECU reset, YES, I would. Easiest way is to simply take off the negative battery cable for 30 seconds ~ 1 minute. That's it, pulling a fuse is more difficult plus chance you could break it pulling it out.

Rokas

I don't understand these forums. Do they work better on the app? I had to make a reply to get to the end. I don't see a list of pages or anything.

I'm just trying to find the answer to my question which is: will the car run with the Coolant Temperature SENDER (not Sensor) disconnected? I know it probably will but I need confirmation. Guys, I know this is a stupid question but I need an answer. Whoever hooked up the old one crossed the wires around eachother so much that I'm afraid something will break and in that case, I need my car to keep running. So PLEASE somebody answer this. I've had this sender for like two months.

spuds

Excellent thread.Im researching everything I need to know before I buy my LS400 so I know what to look for before purchasing and what to expect as an owner.Buy OEM on parts like this sensor for sure,no savings risking aftermarket for this item IMO.

spuds

OK,so I have the ls400 1998.
is this the right part,and is it the real deal? Looks good to currently brain dead me,if so,I will order it.
=============================
https://www.ebay.com/itm/GENUINE-TOY...tY458X&vxp=mtr

Leeroy

Spuds, that's the one I used on my 2000. Worked perfect. My original one was broken almost completely in half. I had weird acceleration when I was making low speed turns before I changed this sensor.

spuds

Thanks Lee.Part ordered @ 29.48 delivered,no tax,no shipping charges.

Did you pull battery neg or pull ecu fuse? I see do it,and dont do it on thread here.

Leeroy

Not sure it makes much of a difference either way, but I tend to err on the side of resetting the ECU any time I change any sensor part on my car.

spuds

OK,will do,thanks.

tango72

mine is not in that location 98 lexus ls400

kelby2fye

I’m 17 and have a 98 ls400. This job was easy to do on my own. Sadly, I forgot to switch the washer onto the new part but nothing is leaking out yet. If it does, I will go back and redo the job. I instantly gained about 3 mpg so i’m sitting around 15. That’s still not what I want so i plan to do a few other improvements as well.

Wesley227

He has every right to call him out if that’s the case of other dude mis informing someone who comes here for help because they don’t know how u got to understand u know about this and it sounds ridiculous I get but I agree with him, if ur the unfortunate soul who comes to get that information and gets the wrong info... Lexus ls400 98 mine reliable last another 20 years... you bet ur *** this website should show the right **** only thing it’s missing is a better playform this website still based the year the flagship came out! It’s only thing that Lexus people have when it comes to **** hard to figure out! I myself end up finding out the 02 sensor that my meter is reading bad circuit 2 bank 2 Is on the passenger side below the door under and coming out the exhaust and I just was lookin at other damage made from the hit to that side before I had it by a deer going 80 it’s Like the impact paralyzed that side of the car but my o2 sensor driver side 1st one is good no problem I’m hoping performance picks up and on to my next challenge a power steering pump... blower motor fan **** no time to fix it headlight and fender fix only problems everything else still rocking! I look a both and the the one on passenger side is very screwed up so that’s one thing I have to get done if anyone here knows where I can find one cheap hell if it works better with a Lexus 02 I might as well buy the right ****! I don’t see any why any ole sensor wouldn’t work hell all it does is pick up the amount flow to tell the computer to pump more or less air in along with fuel which is the very reason any vehicle goes so I’d like to fill up an not run out of gas in 4 days time anyone with suggestions throw em at me I have a basic plan but any cheats or other Lexus diy knowledge we can trade! Owning this car turned out to be owning a rare vehicle that will never quit

YODAONE

Observed the black plastic connector portion of ECT sensor sustained unexplained separation from its brass base on my 1999 LS400...




Image depicts oxidation between the probe base and plastic connector. Probably should be sealed...


See:

https://www.clublexus.com/forums/ls-...l#post11207635

The 1990- 1997 design appears more robust with raised brass turtle neck collar to support the base of green plastic plug.

My question is whether anyone knows whether 1990-1997 ECT sensor will interchange with the 1998-2000 sensor.

Thank you.

Thanks.


1990 - 1997 ECT sensor feature a raised collar which the green connector shell nestles.

This is 1998 - 2000 ECT sensor. Notice the brass collar is missing at junction with exposed plastic base...so no lateral support. Someone might not have thought this one through.

400fanboy

Can I please get confirmation on my diagnosis? Thank you.

Poor gas mileage, bad when it's cold outside, worse when the car is cold & MUCH WORSE when the car doesn't warm up properly because I only drove it for 4 minutes.

14mpg is typical for around-town, short trip durations (5 minutes).
20-22mpg is typical for 50\50 local\highway driving with much longer trip durations. Some short trips, but some hour + long drives.
24-26 mpg is observed on a long road trip of pure highway driving @ 75mph average, with winter tires.

I've checked the computer, it's accurate (to within a few tenths).
I drive reasonably conservatively, so I expect to see the higher spectrum of fuel economy of what this car is capable of.
While it doesn't eliminate O2 or MAF, these are far less likely as those would typically give problems across a broader spectrum than just engine cold-start.
Rich exhaust smell when car is cold, smells normal once it's out of open-loop and cold start procedure.
Engine runs and feels healthy at all times. No running issues when it's cold or warm. No check engine light, no codes, no unstable idle, no issues starting.

I don't own a scan tool, because I'd love to know the ECU indicated temperature when I first start the car, along with what the fuel trims are doing. So I ran an idle warmup test with the following conditions.

Car parked in garage, garage door open so I don't die lol, cabin heat on. Ambient outdoor temp 30f, ambient vehicle temp in the garage 40f.

T+0 seconds start car. Exhaust smells very fuel rich.
T+10 seconds engine idle: 1200rpm, stable
T+90 seconds heat starts coming out of vents
T+3 minutes max heat from vents, air is very hot and stays hot
T+5 minutes coolant needle starts moving, it had been resting on max-cold this entire time
T+6 minutes idle starts lowering in sync with coolant needle rising
T+7 minutes coolant needle crosses the cold line
T+7 minutes exhaust doesn't smell rich any more
T+10 minutes engine idle 900rpm, coolant still indicating close to the cold line
T+12-13 minutes engine reaches normal idle (800rpm)
T+17 minute the car (finally) hit normal operating temperature as indicated by the needle


Suggested failure: coolant temp sensor. Most likely an offset failure where the sensor reports incorrect values, colder than it is, but not cold enough which would cross thresholds in the ECU indicating sensor failure and throw a code.

If the engine runs extended period of time in cold-start procedure, in an extremely fuel-rich condition, would explain the poor fuel economy and rich exhaust smell when car is cold and only when it's cold. Failing MAF would have documented issues at full throttle or idle and would be unrelated to engine temperature. O2 sensor would cause fuel economy issues even when car is warm or would be "sluggish" to react to changes.

Am I correct in this diagnosis?

1998 LS400 - 89422-30030.

$70 shipped.

LeX2K

I'd lean more to you needing a new thermostat.

400fanboy

What are the the things that suggest that? The thermostat isn't stuck open or closed because that would be obvious? What suggests thermostat over CTS. Or does this symptom list also suggest a sluggishly responding, but otherwise correct thermostat, which causes the car to stay in cold-start for longer, but will otherwise not overheat or over-cool.