The ECU connector is NOT a normal Torx fastener. It is a 5 lobe and not 6 lobes as a true Torx screw has. You can of course replace it with any screw with the correct thread and length. Jag probably did the oddball screw because 20 years ago ECUs were being stolen. Not a concern now.

 

I'm aware of the special pattern, I can confirm that I have the right tool (but the previous owner clearly didn't ). But good to know the reason behind this choice from Jaguar. I'll look for the same screw but if I cannot find it, I will put something else instead.
Concerning the others missing screws, can I find general schemes or bolt lists somewhere or I have to figure them out one by one?

 

Probably figuring out bolts and screws is one by one. If you can narrow it down to a certain system you can try parts diagrams for instance on SNG Barrat or other parts suppliers. Simple if the bolt or screw is the one holding the alternator on but impossible if you are looking at a hole under the air cleaner where you think there might have been a screw once but no idea which part diagram it might be on. I hope that makes sense.

 

Yes, it totally makes sense, thank you. SNG Barrat seems to have really good diagrams.

 

OK, i did my testings according to the following instructions, and i seem to have an ECM problem. The thing is I can't start the car anymore... My battery charged all night, has 12,67V, and when i try to start the car nothing happens and the screen seems to be in a loop. What did I do wrong?
Additionally, on T1 I don't have a voltage anymore when it was correct before all this. I suppose it is linked. Thank you on advance for your help. (I only see that right now, but maybe I should rename the topic? We are a bit far from the original concern...)

 

Fyi I have the "communication fault please consult your dealer" message. I can't crank the car, I can't get out of parking mode and the car won't honk, but still does if I try to lock it without closing the door.

Edit: I can't read obd codes either. The module says it cannot connect to the ECU...

 

Udpate, I cleaned the plugs I touched and tried to reinitialize everything by letting the positive and negative connectors touch overnight but i didn't do anything... I'm a bit stuck right now.
I suspect it may be a loose connection of the ECU connector but I have no idea how to remove completely the 5 star screw in the middle, since it turns freely in the plug...
Any guess?

 

Do you need to remove that 5 star screw? Another user suggested a flat head screwdriver with a notch cut into it for clearance around that little pin in the center. I understand from the pictures yours is beat up pretty badly but you don't need much torque on that screw to assemble the connector so a modified screwdriver would be enough.

It looks like there is a captive washer on the inside part of the connector that engages the threads of the screw. I think it just turns with the screw by design so the screw never falls out. I would try and hold that in place while turning the screw. There are 6 little holes where you could try and grab it with a pin or a piece of stiff wire, maybe something like a paper clip (today I learned "paper clip" translates to "trombone" in French). You may be able to remove the screw that way.

If you still have a communication error once you get the ECU connector seated correctly I would try it again with the throttle motor/position sensor disconnected. It seems like you had problems there so that might be grounding the power and the ECU is misbehaving because of that.

 

Too Late

I had the time to discover that this washer is called a Starlock washer and is virtually impossible to remove in this position. It is not threaded and the general procedure to remove those is to pry it open with a needle nose plier or to cut it with a dremel. Not enough room for that. The best way in my opinion would have been to push the screw through the plug with a press but I don't have one.
So i decided to drill the head and extract it with a regular plier (some small pieces of red rubber came with it, I don't know what it is).
Now I'll order a new screw. For future reference, the ECU plug screw is a M6x54mm with only the last 10mm threaded (turning clockwise to tighten) and a 5 star 30 pan head with a security pin in the middle.
I'll update if I am wrong on that.

Once I seat the ECU connector correctly, I will try what you suggested, thank you

Edit: Since the head is not attached to the screw anymore, my measurements can be off so I'll bet on a standard M6x55 rather than a weird M6x54.

 

Nice job getting that out. Since you were drilling at the ECU connector I would blow some compressed air around and in the connector to be sure you don't have little bits of metal floating around in there.

 

I have already vacuumed everything but compressed air is a good idea. I'll remember buying a can next time I go out for groceries

 

I just received the new screws, and the car started!










Now I can confirm you that a regular (ISO 7380-2) stainless steal, pan head, Torx M6x55mm is a good alternative for the ECU connector if you destroy the original
Time to go back for more testing...