lexsc4

Hi all,

08 RX350 with ~100K miles. Two weeks ago the Check Engine/TRAC light were on, VSC light blinks, so I tightened the gas cap, and pull the negative and cleared the code. Hoping this is just a gas cap issue.

2 weeks later all those lights are back again, so my mechanic pulled the code and came up with P0128. He told me it should be the problem with the Coolant Temperature Sensor. Has anybody had this issue before. The water pump, thermostat was replaced last year and coolant level is OK. No issue with coolant temperature and the car drives like normal. My mechanic cleared the code and told me to drive it again until the lights come back and he will pull the code again.

Any other advice before I buy the Temp Sensor and have it installed?

TIA.

08 RX350 AWD (wife)
08 Avalon Touring (mine)

Kamote7

Same problem with my RX330 2005 have trouble with thermostat and damage the radiator eventually replaced both but check engine light trac/VCS lit up not yet sure what's wrong thanks for your help

lexsc4

Thx. Just replaced the thermostat, Coolant temp sensor and radiator. $450 lighter now and no more lights.

lexsc4

Try to get the code first. Maybe change the coolant temperature sensor.

Savnout

Same code, have reset 2x's now tech stream...it seems to last about a month til lights come back on (CEL&VSC). Have noticed since we got it last year that the temp always seems to stay below normal operating temp. Which I know is not great for emissions...but kinda like it running cooler.

Gonna replace this weekend (thermostat) should be a easy, cheap fix. If lights come back in will hunt down the coolant temp. Sensor.

Sav

lexsc4

One advise. Get the OEM thermostat. My mechanic tried to save money and got the aftermarket. Temp continue to raise, he replaced it again with OEM and everything works perfectly.

lexuswoo

Just went through this. fvsc and cel on. p0128 code. first i changed the temp senosr. and the gas cap. cleared ligts but they came back on after about a week.... Sooo. i did notice that the temp was low so maybe the -0128 code is correct.
finally changed the thermostat and cleared the codes. the temp is back to normal. will see if the codes come back .

Hints on changing the thermostat. I could not find any on you tube for the rx 330. One of the videos was totally wrong about the location.

It is in the same position as the 3.0 v6 found in any camry or equivalent vehicle. Luckily I had done a camry 3.0 the week before. It is a pain to do. Lousey location , little room to work.... difficlult to see all three nuts that hold the thermostat housing.

It is on the driver side. you have to remove the air filter box and associated hoses, and wiring in order to have room to get at the thermostat housing.

You do not have to take the starter off. One video claimed that you have to in order to acess the housing. wrong....!!!!!

If you can get a new o ring for the tube that goes into the thermostat housing. has to be bought at a dealer. the local autoshop doesnt carry them. if the old one rips or is too worn, you will be stuck.til you get a new replacement.

A magnetic ten mm socket would help greatly. dropping and losing any of the three nuts that hold the thermostat housing is easy to do. I had to use tape as insurance to not lose the nuts for both removing and replacing.

Give yourself 3 to 4 hours to do this job. It can be done but its not a fun job.

good luck.

Savnout

Thank you for the response. Yeah, I saw that video in you tube from club Lexus and have been putting off the thermostat replacement because of removing the passenger side tire, panels and serpentine belt.

I just replaced the temp sensor and that didn't solve the problem. I DID think the thermostat was on the passenger side...Next to the temp sensor. Are you sure it's in the driver's side? I was thinking that was the lower radiator hose. The upper hose on mine is on the passenger side.

​​​​​​Now, when I bought this car it was missing a gas cap...The dealer went over to autoZone and got a cheap replacement which does click when I put it on..But it's def. Not factory.

The car does run about 10° cold all the time. Thinking someone replaces this thermostat and it was a fail-safe model and failed stuck open or just is stuck open.

So your saying my 2004 RX330 AWD model the thermostat is on the driver's side under the airbox?

Thank you for your reply,

Sav

JoeInHNL

I just did mine (2004 RX330), it is on the driver side as stated above. The lower radiator hose goes into the inlet pipe which goes into the thermostat housing.

I removed the inlet pipe and thermostat housing together. I did not break the joint between the pipe and the housing. I pulled the starter. It is not hard and gives you a lot more room to work if you pull the pipe and housing together as I did. I used a magnetic wand to remove the housing nuts once the were loose and used the wand to start the bolts.

The o-ring between the pipe and housing is available from NAPA.

Ldemon83

It's one of those lexus things man. It happens to me every once in a while too. I find that when it does happen, its usually after I leave the gas station. Im guessing it has something to do with the gas cap not being clicked the whole way in, and the computer reads it as such, causing the check engine and VSC lights to come on.

lexuswoo

savnout

i sent you a reply on your email. sorry, just got time to check my mail today. Let me know if you have any other questions about the thermostat.

For others that might need to know how to replace the thermostat....here are some hints.

the air filter box has to be removed. I also had to take off the front trim pieces that are attached to the air filter intake stuff.

I didn't drain the radiator.. I just took off the hose that is attached to the tube that goes into the thermostat housing. I lost about half a gallon. that i collected with a big pan.
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I also took off the little hose that is just above the thermostat housing. This will then allow you to see all three 10 mm nuts on the thermo. housing.

If you use a good light and climb right on top of the thermostat housing you will be able to find and see all three nuts. Have someone help holding the light and guiding you to the nuts.

You need a bunch of assorted extensions to make it easy to get to the nuts.

You can lose and drop the nuts easily. so..use a piece of tape on the inside of the 10 mm socket so that the nut is held on tightly for both removal and replacing. a magnetic 10 mm socket would be a great help...but i didn't have one.

It is a pain to get all three nuts...but it can be done with some patiience.

There is a wiring harness plastic holder that is screwed onto the thermostat housing. It was a pain to figure out how to disconnect the electrical plug. I eventually had ended up messing up the holder by the time i took it off the thermostat. It has to be removed in order to have room to take out the thermostat.

I would recommend that you go to lexus and get a new o ring for the tube that goes into the thermostat from the radiator. Mine leaked a little when i put it together. had to take it apart and reseat it just right so that it wouldn't leak.
a new o ring would have made a tighter seal.

HInt....after putting the thermostat back together and the hoses....fill your radiator back up to see if you are leaking at either the thermostat housing or the tube that goes into the thermostat housing. If you have crimped the gasket on the new thermostat....it will leak....if you didn't seat the o ring on the tube correctly...it will leak.

check for leaks before putting the air filter back on....just in case you have to redo something.

good luck...

lexuswoo

update...

I had the vsc and the cel indicators coming on when i started this problem. along with a po128 code. changed new temp sensor.....came back on after a few days.....changed gas cap.....light came back on
after a few days.....


finally changed the thermostat.....been a week and 300 miles so far. no more lights on. I guess it was the cool running caused by a bad thermostat.. temperature gauge is back to the normal position as opposed to being down between the first and second lines.


f

lexuswoo

update. so its been two weeks now and about 500 miles. cel and vsr light are still off. guess it was the thermostat and a low engine temp that caused the p0128 code.