"BMW X5 - Display - Multiple Warnings at the Same Time"

By Ron Stultz

26 April 2012

Summary: as the BMW X5 is "electrically controlled: onboard computer, sensors, etc", a failing or low charge battery results in multiple display warnings and even, perhaps, Transmission Fail Safe.

Background:

BMW X5, 4.4i, model year 2000, 168,000 miles.

2 year old AutoZone Gold battery. Huge, heavy.

PriorityStart battery voltage monitor installed to keep a parasitic drain (ignition off drain) from completely discharging the battery.

Multiple display display warnings:

Recent trip, 200+ miles. 4 hours of rain: headlights on; wipers on; radio on and cabin climate control blower running.

10 miles from home, X5 bucks a time or 2 like it out of fuel and then "Transmission Fail Safe Program".

Also get all warnings related to brakes and traction control (Christmas Tree as it is often referred to).

But X5 picks up again and "Transmission" display disappears but transmission will not go into manual mode.

After a few more minutes "Service Engine Soon" alert displays!

Make it home.

Turn off X5 and then start it up.

All brake related and traction control lights disappear as soon as I drive couple of feet.

Next day, attempt to attach scan tool but can not synchronize with onboard computer.

Start X5 and after a few minutes, it completely dies and will not start like battery dead.

Check system voltage and battery literally has no charge.

Disconnect battery  from X5 and fully charge it.

Reconnect battery and X5 fine! No warning lights, no "Transmission Fail Safe".

Have battery checked and it tests ok although upon examination, one cell low in water/acid.

Add some amount of water to all battery cells.

Monitor alternator voltage and appears to be charging (13.8 volts which is low but a valid charge voltage).

Mystery at this point why battery drained down. Rain for 4 hours?

Alternator failing? (1st alternator failed around 100,000 miles)

Going to drive for a while and monitor battery charge.