2006 S Type. Had a "Cruise Not Available" message with no warning light or codes and occasional rear brake light warning for while now. New battery fixed the problem. The PO claimed the battery was new when I got it 3 years ago. The date code on the battery was 2006. Not bad for a 10 year old battery.

Great fix!

(It's not the guaranteed fix for the fault, but hey since when was a fault only able to have one cause.)

I'm certainly no expert with these cars. But I do own 3 of them and am constantly troubleshooting one thing or another. I've learned from experienced, knowledgable forum members like JagV8 that a weak battery (even a new one) is always the first suspect when multiple, seemingly unconnected codes appear simultaneously. A "Curise Not Available" code is almost always a tipoff to a battery issue in my experience.

I've learned to ALWAYS ensure my battery is fully charged before troubleshooting any codes. I do this by regularly connecting my Battery Tender charger and topping up my battery. This isn't a sales pitch. Several forum members from different parts of the world did research on battery maintenance, the link to which is in my signature below. I'd encourage everyone to read it. It's not as dull and dry as it sounds.
Steve

That was the first thing I checked, the resting terminal voltage was OK 12.6 V and the battery held its charge. When there was no obvious problem, I had a load test run on the battery and it was OK until around 100A then the terminal voltage dropped to 8V...... I should have looked at the date code first, the battery was well past its useful life. I got a Duralast Platinum H8 AGM in sale for $145, Ill see how long it lasts.