This warning commenced during last year not long after rear diff bearings replaced. Austen ( at Bell Eng) and others thought it could be related to voltage drop in the car battery (which was some 8 yrs old at the time). New stop start battery fitted last year and the problem (warning) did not display - until this week when it displays on some occasions. Incidentally sat nav has also randomly started to show "unable to read disc" at times. Any thoughts?

I don't think the problem of not reading disc is related to the battery but rather the laser len inside the DVD unit is dirty. Sometimes you can fix this problem by a cd/DVD lens cleaner disc. I don't have answer to the intermittent transmission problem, a faulty code may help pinpoint this problem.