Sitting on top of the valve body are two revolution sensors mounted and connected to the TCM circuit board. The sensor most forward to the front of the vehicle is called the Turbine Revolution sensor 2. The next one back is the Turbine Revolution sensor 1. These sensors poke through a hole in the case. Figure 4 show them as seen from inside the transmission with the pump and drums removed. The sensors appear just slight behind the band.
Bear with me for a moment as I explain who reads what. Once I get through this I will be able to simplify it to terms we can use practically. Ok, here we go: Turbine Speed Sensor 2 (TSS2) reads the sheet metal windows attached to the front planetary sun gear shell. Turbine Speed Sensor 1 (TSS1) reads the Input housing planetary shell that is attached to the Turbine shaft.
Now, what does this basically mean? TSS1 is an actual turbine shaft speed sensor that will provide a turbine RPM reading anytime it is in rotation. The TCM uses this to determine transmission gear ratio against the OSS rpm sensor. It also determines converter clutch slip against the ERPM sensor. So it’s a typical TSS/ISS. However, TSS2 reads the sun gear in the front planetary assembly.
This drum is held stationary by the Front Brake Band for EVERY gear except fourth. This is the only time you will see an RPM reading from the speed sensor. This means code P1716 sets when it does not see an RPM reading at the time the TCM command fourth gear. This could be due to a faulty solenoid or a stuck valve. This is critical to understand otherwise you might be dropping close to a thousand dollars for a new TCM and valve body. Be sure to exhaust all other possibilities before committing yourself to this purchase.
It is interesting to mention that the Front Brake Band is controlled by a Front Brake band solenoid. What is odd about it, this solenoid remains ON at all times except for fourth gear. At which time the solenoid turns off and the band releases. I would have thought to turn the solenoid on when I need to release the band. Especially since it is only applied in one gear; fourth.
Of the entire rack of solenoids on the valve body, this is the only one with a rubber seal between the circuit board blades and the solenoid. It appears that since this solenoid is on near 99% of the time, it could get a little warm. It certainly is subject to failure as a result of it (P1716). I suspect this rubber seal is used in an attempt to prevent capillary action pulling fluid into the TCM’s command center. Its just one of those things I scratch my head over wondering why. I would enjoy speaking with the engineer who designed as they usually have good reason. I can only speculate.
