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It has a trouble code P0116 (Engine Coolant Temperature Sensor 1 Circuit Range/Performance).
I was able to observe through my OBD2 scanner (BlueDriver) that the engine coolant temperature doesn’t read higher than 145F after more than 30min of driving (mixed highway and city) and the temp gauge also reads low.
My first assumption was a bad thermostat so I purchased a new Denso thermostat and pink super long life coolant, but then I realized my assumption may be wrong.
I figured the coolant needs to be replaced anyway after 11 years, but I want to do more diagnostic work. How can I verify the validity of the temp gauge? Is it possible the actual temp sensor is not reading correctly? How can I check that sensor and where is it located?
Any tips or help would be greatly appreciated. Thanks!
p.s.: I have access to Techstream software as well.
Update: New thermostat fixed it. Also helped complete the emissions monitors that wouldn’t finish after more than 200 miles prior to repair.
Follow the upper radiator hose. Where it meets the water outlet on the block, there is a sensor right there on that pipe. That's it. It is pretty much directly above the flywheel.
Follow the upper radiator hose. Where it meets the water outlet on the block, there is a sensor right there on that pipe. That's it. It is pretty much directly above the flywheel.
I think mine is actually on the back of the engine at the water inlet from the bottom radiator hose. This RX has a 2GR-FXE, very similar to a regular 2GR-FE.
I found a service manual guide on how to access it and test it.
I’m thinking of using a temperature gun to measure the lower coolant hose (after the thermostat opens up) and compare it to the OBD2 ECT data. Then if it’s inaccurate, I’ll remove the old sensor and test it in hot water for resistance values, then compare those values to a new one.
These are the resistance values you should see on a working sensor. Some general info on how to get to the sensor on a regular 2GR-FE V6. Sensor location
ECT sensor tested okay, but I still replaced it. Interestingly the new sensor was less accurate at room temp 20C(68F) than the old one, but once they got to 80C(180F), both had the same resistance values.
Found the thermostat was stuck open and wasn’t moving at all in hot water. Got that replaced, tomorrow I refill the system and find out if it fixed my issue.
Draining the engine block was super easy, love that this hybrid doesn’t have a front differential in the way like the regular RX with AWD.
Getting to the sensor required the removal of air intake piping and all the engine bay covers.
Getting to the thermostat required the removal of all the engine bay covers, disconnecting the main engine harness and moving the connector out of the way. The thermostat housing is tricky to remove with one blind nut, and limited access with a hard AC line in the way, so having a small inspection mirror helped understand where everything was.
Radiator drain. Front engine block drain located right behind the AC compressor and the oil dip stick inlet. I remove the 12mm bolt holding the dipstick tube and swung the tube to the side to give me access. You can just about see my empty vinyl hose in the middle left. Did this one last and barely anything came out. Rear engine block drain right above the passenger axle shaft Engine harness disconnected and moved out of the way. Plastic bag is covering the computer and a latex glove is covering the harness connector. Thermostat housing Old thermostat stuck open New Denso thermostat New thermostat in place Intake piping and engine bay covers removed. ECT sensor is right behind the inverter. ECT connector unplugged. Located right in the middle of the V at the back of the engine next to the heater hoses. Old sensor removed. 19mm wrench required. My deep socket bottomed out and couldn’t reach the nut.
P0116 Engine Coolant Temp Sensor 1 Circuit Range/Performance
