Hello. I have a 2002 XK8 with 15,000 miles. I have had the car for 10 years and have a nagging problem: the transmission works fine unless I use it to downshift such as when slowing to a stop from Interstate speeds. I may drop it one gear or two. About 50% of the time when I place the gear lever back into the normal position (D), I receive the "Performance Restricted" message and indeed the cars acts as if it is "Limp Home" mode. I can clear it by turning the car completely off and then restarting it.
Is this a mechanical or software issue?
Is there any "fix" for this?
Thank you,
Bill

 

Has the gearbox been serviced? The ZF 5HP24 should be serviced with new filter and fluid every 100,000 kms/60,000 miles or five years.

What is the voltage across the battery terminals with the ignition in the OFF position when checked with a voltmeter?

 

With only 15,000 miles (and 8,000 when I bought it when it was doing the same thing), I've never had it serviced.
As it's always on a battery tender, I would assume it's voltage at rest is around 13-13.5 volts.
Bill

 

Might want to check that directly. A 10 year old battery (or older) on a charger is still an old battery.

I assume that other things have been serviced over the last decade?

 

^^ What he said....