Apologies but I don't have time to look at the schematics, but I seem to remember pin 40 or 41 being important.

 

No problem, I will document what I find here for my own tracking.
I saw another person had similar issue Unresponsive ECM on a 2003 S-Type 4.2L s/c (Fixed) - Jaguar Forums - Jaguar Enthusiasts Forum
It is lucky I like puzzles, I hope to solve this one.

As I thought I had a corrupt ECM, I saw one on eBay last week so for $150, I ordered that, which arrived today.
Installing that, and powering up with apprehension, instruments powered up, but NO ERRORS were displayed. PATS light was on steady.
Engine did not crank but that was expected as it would have been invalid VIN.
So I thought, this requires the immobilization programming and followed like the post above.
Disconnected OBD
Entered VIN
Loaded config
Connected
Went to write to ECM and it crashed out and failed to progress and also became non responsive.

So now I think that the SDD build or Mongoose I have is failing in some way.

More research, but it I suspect then that the vehicle is probably OK and I have now a SW issue.

 

You can't just swap ECMs on these cars. IIRC, it takes more than just the immobilzation programming to introduce a new ECM. The VID block data has to transferred to the ECM, and I never found out the exact procedure for how to make a different ECM play nice.

 

Well, I have finally converted my 2 tonne brick back to a desirable driving machine.

After trying a couple of Mongoose & Mongoose Pro clones, and a VCM Clone, and various versions of virtual machines and software IDS and SDD going from V118 through to V135 and none of them working, I bought an original Drewtech Mongoose Pro JLR adapter and plugged it in and programmed and reinstalled the ECM and VID set ups and removed all error codes.
In spite of fears from various Jag tech notes about VID block rebuilds and secret keys, none of that was required and the software, when it works right, could build the VID Block and sent to the ECM, when the interface works properly.

I now know how to monitor the processing log and look for errors and the differences between the CAN bus and the Serial bus and so much more.
I am sure there is much more to know, but that will be on a need to know basis.

After standing forlorn for 2 months with no brain, it started right up, and was just as it was, no errors, although much, much dirtier.
Now to go and give the old girl a good bath and reacquaint myself with her pleasures.

I hope I can return some of the help I received to others, but would not wish my troubles on anyone else...

Thanks to all that helped provide consults and guidance.

Anyone need a known working Mongoose cable for ECM programming. Rental available

 

Interesting thread, so what turned out to be the root cause, was it ultimately caused by the low battery?

 

While i am not keen to try and repeat the process, i believe the flat battery was a coincidence. While it was flat, it was the day after having been messing around with SDD, and not knowing enough at the time.
I had been updating some basic settings like mirror tilt, door arming etc. I ventured into transmission addaption clear, and service campaigns. When running one of these, the SW threw some abort error. I left it alone and thought all was ok, but after overnight, and dead battery, I had all errors. I now believe that the abort, either killed it, or it ECM was cleared, but then not able to be programmed due to the poor programming cable. It is my belief, that I did drive it after the error, as i thought I might have had killed it, but may not have or I went back to trying to do other connections, thinking I could not kill it, but did subsequently.