Checking the battery in my 01 XJ8L I get an engine-off reading of 15.6 volts - could that be right? I expected just about 12.6 as acceptable.

Is this a problem, maybe the wrong battery? The OM doesn't offer any clues as to proper battery spec and neither does AllDataDIY.com.

I need to rule out battery problems as a cause of warning light issues (ABS/TRAC).

 

OK, that was dumb. My meter battery was low and with a new battery in the meter I am reading 12.49

 

Look up Occum's razor on Google.

 

Yes, well I can rule out the battery having replaced it. I suppose Occam would just take it to the dealer...