Simply crusing along I hear a mild thump (as all systems shut down) and then the computer starts flashing all the worst warnings - transmission out, safety mode on, ABS out, etc. Limp home mode is simply idle - I need to pull off the road, shut down and restart and everything is fine again. Sometimes for days, sometimes just for a few minutes.

Could my computer be going out?

 

Of course, I should have added 2000 XK8.......70,000 miles

 

Probably not....sounds like the relay for the ECM is getting dodgy or there is a bad connection or damage or corossion in a main harness.

 

initially, that is what I would think...ECM issue

 

Where do they hide the computer in the XK8?

 

The Engine Control Module is located in the 'firewall extension' on the right side of the engine compartment. The Transmission Control Module is in there also so you don't get them confused. The ECM power relay is the one in the fuse panel box. Swap it with another like relay. Almost all the relays in the car are the same.

You can get a copy of the JTIS, including the electrical schematics at this link:

https://www.jaguarforums.com/forum/s...ead.php?t=9933

With all the erratic codes and messages it does sound like a power, or ground, issue associated with the ECM.

It is always a very good idea to disconnect the battery ground cable before messing with this car's electrical system.

 

Thank you

 

Good luck! Let us know.

 

Check the main Electrical Feed to the Engine Compartment. It is a Terminal (protected by a rubber cap) mounted near the Firewall beneath the elbow of the L shaped Air Tube feeding air to the Throttle Body. A loose connection can cause the symptoms that you describe.