J Gate and sport button illumination

[new2jags]

Battery flat on my 53 XK8. Trickle charged it overnight, and started on first turn. Amber 'check engine' light remained on, until local garage reset same with a magic box, stating it was a an engine memory fault. Returning from a 50 mile run, noticed the red illumination light of the J gate gear selector was flashing, and the sport button light was not activating. Maybe my imagination, but I don't think the manual shift side of the J gate was working as it should either. Any ideas?

[mike020150]

XK8 electrics are complicated and highly sensitive to battery condition and voltage. Hence, first you need to know why the battery went flat. If there is the slightest doubt about its condition, you will need to replace it with a good quality unit meeting or exceeding Jaguar's battery specification. Do not be tempted to use a smaller battery even if it fits in the battery tray (there are usually two positions provided). If, after sorting the battery issue, the symptoms persist, you will need the services of a Jaguar dealer or Jaguar specialist (eg David Marks) with the appropriate diagnostic equipment to stand any chance of achieving a firm diagnosis. I'm afraid XK8 electrics are not DIY friendly. Mike.

[new2jags]

Thanks for that Mike. I appreciate the intricacies of the electrics, but I hadn't started her since Christmas, so I'm guessing lack of use was the problem with the battery. Still doesn't explain the flashing lights and apparent defect in the 'manual' gear shift. Open to ideas!!

[mike020150]

Many of the XK8's electrical components only work providing battery voltage remains above a given number of volts. When a battery can't provide that voltage, the component can generate a fault code and/or warning lamp and/or cause the control unit to enter a state like 'limp home' whereby only limited performance/gears will be available until the fault has been corrected. The complexity of the car's electrics means that many strange combinations of codes, lamps and apparent malfunctions can be generated by something as simple as a battery in poor or near failing condition. Mike.