Replacing the Engine Temperature Sensor
 

I have wanted to do this for some time now. Mine has not failed nor do I have any codes but from what I learned from the LS400 and the forums is they don't tend to fail like this. They basically start sending incorrect signals to the ECU. Misreading the correct engine temperature, which affects mileage and performance. Couple pics of the sensor. Trying to figure out who makes it. It's not Denso. The mark looks like Tie or Tiej. I don't know.

Do I need to coat the threads with any kind of additional sealant? Any other suggestions?

Funny you brought this up because i am chasing a low idle problem, and after exhausting all the other maintenance items, i'm thinking of giving this a try. I also have been reading the LS400 forums about how all there ECU go bad. I;m glad we don't have to deal with all that nonsense. Throw that puppy in and give us and update:D

id prob use some antiseize on there just in case. but i throw antiseize on anything i remove now due to NY's healthy usage of salt.

No additional prep necessary other than making sure the threads on the intake are not obstructed. The LS400's had a copper washer/gasket. Looking at Sewell the part # has been superseded:
What they show is:
Water temp sensor EFI: #8942230030.
Gasket #: 9043012005

For others, verify prior to ordering:
http://lexus.sewellparts.com/oem-cat...S430-2004.html

You need to use some kind of thread sealer like ptfe on anything that goes into water or oil. If you have a washer or an o ring, you technically don't have to worry, I still like to use ptfe anyways.

I do have the gasket. I'll let you know any difference. I am going to try to data log the same drive before and after with the my Techstream software.

I've read briefly about the LS400 problem and what's got me worried is that the engine temperature gauge reads normally on the dash, but the signal that goes to the E.C.U is incorrect.

Do we know whether the OBD's engine coolant temperature reads from the problematic sensor?

I plugged in my OBD scanner the other day and it seemed to have a sensible/valid engine coolant temp reading (180 degrees f? ) but if I ever think the sensor is going out, I'd be curious to know whether there's a good diagnosis.

There are two different sensors. One feeds the ECU the other the dash. That's the point, most of the time there is no good way to tell. So come 130k miles or so just replace it.

Correction: there is only one sensor not 2. Older LS400s have 2.

I put in my new engine temperature sensor today. It was actually very easy. Just remove the air tube between the air filter and the throttle body and you have easy access. A 19mm deep well socket will easily remove it. Also gave the throttle body a little cleaning and the little idle port on top as well. I did not know about the port until DockOf-Bay mentioned it. Between cleaning the idle port and replacing the sensor she is really running great. A lot accomplished today. :thumbup:

A few pics of the process and the old sensor. In my opinion, antifreeze really does a number on the sensor and it should be replaced at the 90K service.

Another little trick. To remove the electrical connector insert a small flathead screwdriver into the groove / clip housing. Then you can easily remove the connector by pulling on the body of the connector. You never want to pull on the back of the wires where they are crimped into the pins / back of the connector. This is how you screw it up easily. Things can get brittle and break. You may also find that some of the heat shielding is old and brittle. Some of mine crumbled when touched. Wrap any exposed wire in electrical tape to prevent heat damage. If it is hard to remove the connector you are doing it wrong.

A little comfused:uh: u say it's running great, but I assume it was running great before. Is it running BETTER???? Thanks!

My car has really always ran great. But I am a bit obsessive and really keep her in tip top shape. As far as the engine temp sensor improving anything I do not know for sure. It's just one of those things that is so important in how the car operates that for $50 I'll put a new sensor in there whether mine was going bad or not. They do fail and as I mentioned in the first post often people don't know until a while after. Not normal to get a code for this sensor.

My throttle body was not dirty. Nor was the idle port. Just a bit of carbon. I had my dealer clean it last year. Now that I am doing things more on my own I realize how easy it is to take it off and do it yourself. Even the small investment in the right tools saves you a ton of money. Especially with my man RKW helping us out too. Even easier. Anyway, the car does run very smooth and she is as peppy and powerful as ever. I can't definitively say that replacing the sensor did anything but it is now off my personal checklist and you can see the condition of the old one. I also did a soft reset on the ecu. Just pull the negative for a min and put it back.

Speaking of Batteries

The correct order to take a battery out is negative first, then positive. Installation is positive first, then negative. This is because the direction that power is meant to flow through the electronics and wiring system in a car. Always disconnect negative / ground first. This also prevents a short to ground. Of course with a reset you don't need to touch the positive.

I just want update that after about 250 miles the car just feels smoother and more powerful. I am also seeing a little better gas mileage. Actually, the best I have seen out of the car yet. Mileage changes with conditions of course but I can honestly say that I believe replacing the temp sensor has improved the efficiency and power of the engine.


Edit... So much power now look what my LS can do... ;)

What's happening in this pic? Is it airborne due to driving it fast over a hump or something? Looks abusive to the car. :eek2:
If its just the power from an acceleration attempt from a standstill, trust me when I say that I and everyone else on here will be getting our temp sensors replaced ASAP.

Ah the joys of Photoshop. She is really on jack stands. ;)

Looks like I'm about to launch to outer space. Or upside down in the stream at the end of my friends property...