BMW X5 with serious issues

[Doonbugg]

Hi All, I have been trying to track down what is suddenly wrong with my 2005 X5 4.4. It cranks great, UNTIL you take it out on the road it runs great. The first thing to go is the transmission goes into failsafe mode. Then the dash lights all start coming on and flashing, Then the engines starts running very rough and will not run. When I tried to restart it it was a no go and everything ( including the headlights ) started flashing. I just cleared the computer and reset the dash a couple days ago. I dont know if this has anything to do with it but is was raining both times it did this. It is on the side of the road now and I am kinda out of ideas. Does anyone have any ?

[brucemillar]

I would suspect a battery voltage/earthing issue. You also need to check that the alternator is charging the battery correctly.

Do the easy stuff first and check that the battery terminals are clean (take the leads off the posts and clean them) then refit and make sure they are tight. Next clean the earth from the battery where it bolts to the body in the boot floor and clean that contact area.

Now measure your voltage across the battery terminals. You should see 12.1+ VDC with the engine off.

13.8+ VDC with the engine at running at idle.

Anything less than the above suggests the either your battery is toast or your alternator is not charging the battery.

[upallnight]

Check for water leaks in the cubbies in the trunk and for damp carpet in the interior.

[X5only]

Do as suggested above. In my case I got a specific alternator code. Similar symptoms as yours and then eventually the car would go dead at highway speeds with power steering loss - a very dangerous situation. Fix it ASAP and avoid taking it to busy roads.

[roadriderg]

mine did the same thing and it was the alternator leaking out transient ac voltage to confuse the computers. Check charging voltage max 14 v and check for ac leakage.

[srmmmm]

I had similar experience involving a deep water event that fried the engine wiring harness. The vehicle was still driveable, but the engine and transmission both went into failure mode. The technician discovered none of the harness connectors had any sealant grease in them from the factory.

2002 X5 3.0 331,100 miles
2014 428i 30,000 miles

2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles

1970 Firebird - Under restoration

[upallnight]

Expect more cars with flood problems after Harvey and Irma to show up on the for sale list.