A couple of weeks ago I experienced engine cutouts while at various speeds. 3 over 4 days, 1 time maximum per day. One occurance was at 65 MPH, so dangerous business. Researching this forum I found a post that suggested that an intermittant ECM relay could be the culprit. So I printed out my car's relay locations plan and found the relay to be behind the LHD passenger headlights, outer of the 3 relays there. I swapped the ECM relay with the inner-most relay (AC clutch) and it solved the problem - although my AC was sketchy at best for a few days. I then ordered a new relay for the ECM and put the AC clutch relay back in its place. Two weeks later and no engine cutouts.
$20 fix.

Posting this for those in future with similar issue.

Joe

 

Jaguar XJ 2006 - Suddenly engine stops while driving, mostly slow speed & not on highways. This problem is very similar to yours. I have been having this problem right from the time we bought the car from 2006. We left the car at the Jag workshop several times but they could not identify the problem. They said there is no record of such an incident in the car computer record. It was intermittent initially and then the problem stopped for a long time. Nowadays it happens almost everyday. By any change would you have the drawing & the location of this ECM relay?

 

I don't have a relay location diagram handy, but the location is simple: on the USA spec x300s the ECM relay is the outermost of the 3 relays mounted right behind the right headlights. Just remove the plastic shroud that covers the wiper fluid reservoir and you'll see the 3 relays. The outermost is the ECM relay.

 

Welcome to the forum sunamalia,

When you get a minute, please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST section and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

Thanks. I will check it out