Went to start car on Monday 2003 XJ6 3.0 SE, turned the key and nothing except messages saying Suspension fault and Steering column locked....
turned out to be a flat battery , multimeter showed only 8.9 volts..
Put smart charger on and after 72 hrs it still showed only half charged.

I was about to order a new battery when i remembered i had left the Elm Bluetooth plugged into the diagnostic socket . After removing it the charger showed full charge within an hour.Once started no faults showing...

Now what i would like to know is: would this discharge the battery or was it just a coincidence?
All views welcome.
John....

 

Is the diagnostic socket switched power? If not, then the device could be trying to constantly scan and communicate with other devices whilst its parked. I would still get the battery checked properly though.

 

The Elm diagnostic gets power as soon as it is plugged in even without the ignition switched on..
i have watched the battery since removing said Elm and it is still sitting around 12.3 v at the cigar lighter socket using one of these..



Or testing battery with a multimeter...and 14.6 v with engine running..

Regards... John...