If there is no oil temp sender, how does the ECU calculate it?

So if it’s using the AT temp in my truck, how is it calculated in the MT? Is there a temp sensor inside the manual transmission?

 

No temp sensors exist on the manual transmission.

 

So if both MT and AT Tacomas display engine oil temp through an OBD2 reader, it would seem irrational to me that the AT trucks would calculate it using the AT temp, and the MT would use some other different variables. That seems bunk to me.

I think this deepens the mystery honestly.

 

I think they are modeling the temp and include various variables to account the temp in all parts of the engine.
I do see that a slight increase in RPMs over a period of time is causing a slight temp increase (coolant temp remains the same)

 

My 2cents... Toyota has different models and different applications. It is easier and cheaper to have a code that is more universal to work in all vehicles and access as needed depending on the vehicle requirements. So a performance type vehicle would use the Oil temp in the cluster because that is common, where the Tacoma doesn't.

As for where it comes from, I doubt the trans temp factors to much into it with the wide variations of temperatures an auto trans can have depending on the load. Engine oil tends to be more consistent and tied to coolant temp.

 

Maybe it wasn't meant to be looked at in real-time through an app.
The service manual kind of implies it's a per trip measurement.

 

I just went through full 2gr-fks engine documentation. Zero mention of engine oil temp sensor or engine oil temp parameter used for any engine control system.

I suggest the parameter means nothing practical and the actual temp sensors logging data (intake air temp, coolant temp, a/t temp, front diff temp, etc.) should be the only ones worth paying attention to.

When I get a chance I'll log the parameter against others since I have a m/t.

 

Googled: "How is engine oil temperature measured?"

The oil temperature sensor sends its information to a separate instrument or to the ECU for monitoring the oil temperature of the engine. In modern vehicles, oil temperature sensors are integrated into the oil level sensor.

More:

The oil temperature in the internal combustion engine is calculated using an oil temperature model, which draws upon at least one parameter that characterizes the operating point of the internal combustion engine. The differential value between the modeled temperature value of the oil temperature model and the measured temperature value of the oil, which is measured by the oil temperature sensor, is included as an input variable in the oil temperature model during an iterative calculation cycle of an oil temperature value of the oil temperature mode, said calculation cycle directly or indirectly following the method step involving the calculation of the differential value.

 

So I was looking closely to see if an oil temp sensing option was included in any of the engine lubrication system parts, actuators, or other sensors. The oil level sensor didn't look like it was capable of any function beyond level sensing.

https://www.ttguide.net/oil_level_sensor-880.html

I feel like a temp model would be used because temp sensing in the sump would not be reflective of actual oil temp in the engine under certain conditions. Hence the differential model input of calculated vs measured. However, if there's no temp sensor at all then any model just wouldn't use a sensed temp/differential temp as an input.

 

I wouldn't apply logic from a 15 year old Siemens Agricultural patent application to what Toyota is currently using.

 

Are you saying that Toyota likely uses much much older technology, or that you would expect them to be on the cutting edge?

 

Maybe they sense the temperature using the drum brakes?

 

A word search of the Shop manual shows that engine oil temperature is listed as "estimated."

It provides detailed information on front differential oil temperature sensor and the A/T oil temperature sensor and how to test those. No such information is provided for an engine oil temperature sensor.

Edit: Should have read the entire thread before replying.

 

Touche...
You know, I couldn't find anything in a cursory search on oil temp estimation patent from Toyota that didn't go back to the 90s.
Then again, I did find a patent lawsuit against Toyota that included calculated oil temperature. Toyota won, as the claims against them were deemed unpatentable, so...

 

Well, there you have it. It is funny that the “estimated” oil temperature has a decimal place!

 

To further the mystery.... Lexus produces several models that show oil temp on the cluster, they have the 2UR-GSE V8 engine. Interestingly, they have a dedicated oil temperature sensor (same part number as our diff temp sensor) and thus circuit. None appear to use the oil temp info for anything other than the dash display.

 

Probably a combo of coolant temp, engine load, and RPM I would think. Cant imagine the ATF has any bearing on engine oil temp at all, other than being stable over a long drive and reflecting the same general trends.

Because they needed something to keep us busy and keep our minds off all the "rust" threads

 

Also, does the turd gen have an oil cooler as part of the tow package? If so even more reason that the engine oil temp would closely correlate with coolant temp.

 

Yes, engine oil cooler is included with the tow package.

 

Lots of manufacturers put sensors on test cars and datalog them to find a correlated value and then remove them from production cars to save money.