Why Jags have similar but different ECU part numbers?
For example: 2W93-10K975-EF and 2W93-10K975-TB

They both used on 2004 - 2005 X350 4.2 SC Jags but
EF have code MB079700-9074 and TB MB079700-9520

Does it mean that they ain't interchangeable and we have to stick to our model only?

 

Dunno. Why are you looking to swap in another ECM? They are reprogramable units anyways

 

Well, the main reason is... price. I can buy TB unit for much less than EF

So, you're saying that I can use different extension, which is good new, the bad news,
it need be reprogrammed, something I'm not sure I can do at least, there is good How-to.

What would you suggest?

 

You will not be able to plug any ECU into the car and fire it up. They are programmed to the car. For one PATS would be activated.

As far as flashing you need to find a shop or independent that has Jaguar properity software.

 

Which means, I have to tow away Jag to shop to have ECU programmed?
But what about my old ECU? Can it be re-programmed outside of Jag?

 

Why reprogram it?

 

Very good question.
I started related topic sometimes back and just posted update in there
which would provide partial answer to your question.
https://www.jaguarforums.com/forum/x...2/#post2040143

 

You can potentially have the existing one tested & repaired.

To use another will require careful programming so as to keep the right data and not load any bad data.