Transmission Overheat MIL Code

[sfpcservice]

Hey everybody,

I have a 2004 sienna and I'm pretty sure I contacted Toyota years back and they told me that the MIL will light up if you overheated the trannie. I can't remember what the specs were or what the specific code was. Can anybody confirm this with specifications?

Thanks!

Rob

[Narboza]

The DTC code chart does not show one for high temperature. The four codes (P0710-P0713) concern whether the temperature sensor is working correctly. DTC P0713 is for a high sensor resistance, not a high temperature. See the attached.

[tcp]

I doubt it. There is no temperature sensor on the U151E/F aisin transmission used in the second generation sienna. That is why OBD devices, like the scangauge, can't show transmission temps. Everything I've read indicates toyota didn't add any temperature monitoring to these vans.

Hey everybody,

I have a 2004 sienna and I'm pretty sure I contacted Toyota years back and they told me that the MIL will light up if you overheated the trannie. I can't remember what the specs were or what the specific code was. Can anybody confirm this with specifications?

Thanks!

Rob

[Narboza]

Now that David fixed the attachments, I added the Repair Manual references to my earlier post.

[brian_bp]

I doubt it. There is no temperature sensor on the U151E/F aisin transmission used in the second generation sienna.

The manual sections posed by Narboza clearly contradict this, even stating explicitly that

The ATF temperature sensor converts the fluid temperature into a resistance value which is input into the
ECM.

and providing a mapping of sensor resistance to fluid temperature:

Temperature: C (F)Resistance: k?
10 (50)6.4
110 (230)0.2



The thing that I find interesting is that - as Narboza explained - the Diagnostic Trouble Codes are all related to sensor conditions, not to the fluid temperature itself. There's no "transmission too hot" DTC, because the DTCs are all about the sensor and its wiring, not about the fluid.

That is why OBD devices, like the scangauge, can't show transmission temps. Everything I've read indicates toyota didn't add any temperature monitoring to these vans.

The transmission ECM clearly knows the transmission temperature, and presumably does something about excessively high temperature, but that does not mean that the temperature is available on the OBDII system, which is required for diagnosis of emissions-related systems and is also used for diagnosis of other systems, but need not carry other operating information.


I think the answer to the original question is simply that the light will not go on and there is no code for high transmission temperature.

The implication of the other information is that - short of hacking the transmission ECM - there may be no way to query the system for the transmission temperature; however, the temperature signal could be read directly from the sensor... if only one could do that without interfering with the ECM's reading of that sensor. The ECM could be applying a constant voltage and monitoring the resulting current (which means intercepting and measuring the current without adding any resistance to the circuit), or it could be supplying a constant current and measuring the resulting voltage (which would be easier to monitor). Both methods are used in industrial instrumentation, but I don't know which to expect here.

[Narboza]

The only other transmission temperature sensor references are in the 2004 New Car Features document.

Fluid Temperature Sensor

A fluid temperature sensor is installed in the valve body for direct detection of the fluid temperature. Fluid temperature sensor is used for revision of clutches and brakes pressure to keep smooth shift quality every time.

and

Line Pressure Optimal Control

Through the use of the solenoid valve SLT, the line pressure is optimally controlled in accordance with the engine toque information, as well as with the internal operating conditions of the toque converter and the
transaxle.

Accordingly, the line pressure can be controlled minutely in accordance with the engine output, traveling condition, and the ATF temperature, thus realizing smooth shift characteristics and optimizing the workload in the oil pump.

Other sensors used to control transmission shifting are:

• Input Turbine Speed Sensor
• Counter Gear Speed Sensor
• Throttle Position Sensor
• Mass Air Flow Meter
• Fluid Temperature Sensor
• Engine Coolant Temp. Sensor

The ECM likely does not calculate ATF temperature, but just uses the sensor resistance directly. If the ATF temperature sensor fails (goes high or low) then shift performance suffers and you get the MIL and DTC set.

[sfpcservice]

What about this:

P0218 Transmission Over Temperature Condition

Located here:

http://www.toyotanation.com/forum/sh...d.php?t=148676

[Narboza]

What about this:

P0218 Transmission Over Temperature Condition

A search of TIS returns no results for P0218 for any Toyota vehicle.