Weird electrical behaviour

[Black5]

Hi all,

My E53 has been behaving strangely.Recently it developed a bit of a "stutter" at idle occasionally.
Yesterday, the car threw out a TRANS. FAILSAFE PROG warning, followed by a warning about the ambient temperature being below -4C while starting up. (It wasn't)
Warnings cleared after car started however, and everything appeared normal.
Then later last night the battery went flat and wouldn't tick over.
A battery test indicated only 8V. (Seems pretty obvious so far...).
I jump started the car and tested the charge from the alternator to find that it was providing a steady 14v at 1500 RPM, so no obvious problem there.
After about a minute of charging I stopped the car to check whether the battery was retaining any charge.
To my surprise, it read 12.4v and the car then proceeded to start normally, with the only unusual thing being that the DSC light remained on.

I tried this about three times and started normally each time.

I've driven it about 300km's today and the "stutter" seems more pronounced, but the DSC light has gone off and everything else seemed normal - albeit I was driving with the air-con off for most of the drive.

I have been monitoring the OBD reading for the Battery while driving and it's been consistently sitting between 13.9-14.1v with an aberration occurring when I switched the Air con on that dropped it to 13.6 while idling, and I noticed on one occasion when it "stuttered" that the voltage dropped to 12.4 for an instant.

A check showed that some temporary error codes were thrown relating to an interruption of power. (Probably explaining the TRANS and TEMP warnings).

I'm going to change the battery for a new one anyway, but are there any other suggestions as to what else could be the culprit causing what appears to be a periodic random interruption to the flow of power from the battery?

[Roadhouse]

Welcome to the electrical gremlin club! Plenty of us are members so you won't get lonely!!

I am having similar troubles but a bit more pronounced. Tested many times without any culprit being identified but now dealer has come back saying its the alternator. Will do a fix and see if that cures.

Good luck with your diagnosis.

[jgold47]

Report back after changing the battery...