when I bought this LS, the CEL was on.
and the readout was
check coolant level
thermostat defective
ECT (engine coolant temperature) sensor defective

SO: I replaced the stat - and it was faulty
I replaced the ECT sensor
and verified that the coolant level was ok.

the light was off.. 2-3 weeks, then it is on again
and the readout is:
coolant temp is always low
explanation.
the power train control module verifies that the engine is at a proper operating temperature.

probable cause:
check coolant level
thermostat defective
ECT (engine coolant temperature) sensor defective

AND this has all been done...

Can anyone shed some light on this, I need for the dash temp reading to be just a little higher.

any ideas??

 

How is the wiring harness at the sensor connection? I've seen past discussion that relates to a PO155, O2 sensor error. Usually you'll get the PO125 and PO155 together.

 

check the condition of the wiring to the ECT sensor, also make sure you replaced the sensor the ECU sees and not the one the gauge reads from.

Burping the coolant again is probably a good idea too.

 

nope, just the one

 

I replaced the one up front & on top by the stat, where is the other one?? I'll do it too.

 

Did it look like this? May have replaced the wrong one.

 

this is it from O'reillyL

 

There is a second one lower down lower for the ecu.

https://www.clublexus.com/forums/6669438-post34.html

 

I think that is the same one by the stat...

but I have found 7. INSTALL ECT SWITCH FOR A/C COOLING FAN
(a) Install a new O–ring to the ECT switch.
(b) Apply soapy water to the O–ring.
(c) Install the ECT switch.
Torque:7.4 N·m (75 kgf·cm, 65 in.·lbf)

this is in the bottom of the radiator and is for the fans.. not the dash gauge (I think)

 

the ECTS has 2 wires, the gauge sender has 1 wire. - they are located right beside each other

did you install the thermostat with the burp hole positioned up?

did you use the real OEM ECTS from the Toyota or else the NTC (OEM) one from ebay?

is there a short or open in the ECTS wiring between the ECTS and the ECU connector? (look at yamae's guide to checking for ripple)

 

I replaced the 2 wire one.
yes the jiggle is at 12 oclock
NO I already said I got it at oreilly..

I WILL look for the 1 wire solenoid for the gauge and get one!!

thanks.... if you were not so ugly I would hug your neck (smile) if this works!!

 

the gauge sender, in and of itself, cannot generate a code, it has no connection to the ECU, however I would use the REAL Toyota gauge sender, you need *accurate* info if your car is running too hot or cold

the real Toyota gauge sender is only $15

"it's the stingy man who spends the most"
- Click & Clack, the Tappet Brothers, Car Talk

 

do you have a part number? my car is NOT running too hot or cold, read the AZ code "the powertrain control module verifies that the engine is at a proper operating temperature" and the lead line is "coolant temp is always low" and the gauge stays around the 3rd line on the dash (when warmed up). mine is a 99, can you really tell me where the sender is??

OH, by the way, my dad and his family came from Sand Mountain, poor share croppers. lot of powell's up there. where are you?

 

Got it fixed, autozone was 1st level, went to Davenport Lexus and they read at lower level said bank 1 02 sensor heater was slow to close because of being oil soaked. replaced VC gskts and 02 sensor, no more P0125 CEL light.

 

Do you have an oil leak? I just had to do my lower oil pan gasket. Weird that it throws the alignment off when you remove the cross member under the oil pan.