haku

hey everyone


i am experiencing a p0128 code. The 'check engine' and VSC lights turn on.

It occurs at random times, such as when I'm driving or just starting the car. I can clear it but it comes back every 2-4weeks

I read that it's either a coolant temperature sensor malfunction or thermostat.

I am wondering where the coolant temperature sensor is located in the 2004 rx330? I know where the thermostat is based on this video
also is there a definite way of checking what is the actual problem (coolant sensor or thermostat?) I have access to an obo2 reader and tech stream (ebay special)

Should I be looking into anything else?


edit: on ebay the coolant sensor seems a lot pricier than the thermostat (60 vs 20) I thought it'd be the other way around~

JoeInHNL

I had the same issue about 9 months ago. It was the thermostat.
On my car, the upper radiator hose warmed up slowly as the engine was warming up so that pointed me in the direction of the thermostat. If the thermostat is working properly the upper hose should warm up pretty quickly once the engine nears operating temperature.

The temperature sensor is located near the upper radiator hose connection to the block.
To check the sensor, temperature sensor resistance should be 2.32 to 2.59 kohms at 68 F, and .310 to .326 kohms at 176 F

haku

Should I be comparing the upper hose to the lower in terms of how quickly it heats up?

Do you have any diagrams to visualize?

Thanks for the info

JoeInHNL

I just felt the upper radiator hose as the engine warmed-up. The temperature change was gradual so I was pretty sure the thermostat was stuck open.

I believe the sensor circled in yellow is the coolant temp sensor.