Be aware that the selector needs to be in D or R.
PDU is the PORTABLE DIAGNOSTIC UNIT that Jaguar used up until about 1998.
There are other diagnostic units that will communicate with the TCM.

Due to a limited number of output pins of the TCM, it is not possible to provide the transmission
oil temperature in selector lever positions other than D or R.
When the selector lever is in N or P, the PDU will actually display engine coolant
temperature (obtained from the Controller Area Network CAN) instead of transmission oil
temperature, possibly misleading the technician.
Action:
To check transmission fluid temperature using the PDU, make the following menu selections:
DIAGNOSTICS, TOOLBOX, POWERTRAIN, DATALOGGER, TRANSMISSION, TOT
(transmission oil temperature).
When checking the transmission oil temperature readings, depress the brake pedal and
make sure the selector lever is in D or R.

 

So that is the reason for the weird oil temp dislplay behaviour. It is the same thing too with MB models and I have been thinking how stupid is this.

 

Gravy-Train your question is off topic so lets not pollute this one.
Yes Torque Pro can do lots of things and here is Cambo's original thread as he was the one who posted how to do everything.

Take a look and I am still a fan and user of TP. In addition TP is only $5 and the custom PID's are free. So very cheap to get.
Cambo's TP Instructions
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Hi Gravy Train,

In order to monitor your transmission temperature you will need to:

1. Purchase and OBDII Bluetooth adapter (search for ELM327 OBDII Bluetooth)
2. Obtain the Torque Pro app
3. When you have the above working, you will need to add a custom monitor (PID) and enter the details of the new PID:
   • In Torque Pro go to Settings -> Manage extra PIDs/Sensors -> Click the three dots in the top-right and select Add custom PID or Import CSV file and use the settings from this CSV

NOTE: This will probably only work with 2001 XJR (with the Mercedes W5A580 transmission)