None that I know of, but you should check with a real Jaguar technician with FIRST HAND KNOWLEDGE.
My experience is from over twenty years ago and limited to my first hand experience.
I used a Jaguar PDU I had access to at the shop I worked at the first time I did it.
The second and third time I used two DVMs and achieved the same positive results.
It's certainly more cumbersome than using the PDU but who has access to that now-a-days.
The other advantage of using the DVM approach is you can see if the throttle potentiometer has any flaws.
Usually you will see a drop in voltage.

 

Dears,

Interesting thing happened today - i've disconnected ATS (Intake Air Temp. sensor) and for some time idle got perfectly flat - meaning normal without any kind of errectict moves.
Sensor is new - from Jag Spares. Connection is good and seems to be working.

But after restarting an engine (Without ATS connected) same issues with idle appears once again.

How it can be connected so much..

 

Throttle pot will be 0.6V at idle. There are two potentiometers in the one body and both will be 0.6V. Near pot is the microswitch. That switch will click when throttle closing. That switch is called idle switch DAC10181. With DVM check this switch.

 

There may also be a problem with the ventilation of fuel vapors. Two electric ventilation valves need to be checked.

 

Thank you everyone for your help. Issue solved and was caused by:

1. Damaged O2 Ground Wire (Caused FF44);
2. Damaged ATS Sensor wire

Both of these made mixture waaay to rich, thus idle was incorrect and MPG where really low..
I was sure that technically it was OK - it made my search for a cause a bit easier.

Thank you.