BMW X5 2001 starts then cuts out after a few seconds after changing battery

The first thing that you must do here is to have the systems computer checked for fault codes, it should have a few in memory. the codes are read through the diagnostic port under the dash.

check the negative wire from the battery to the body (not good ground ) clean

Really bad luck. Do you have a obd2 fault scanner? that may help. If this still could not detect the problem, send your car to a local garage. Good luck!!

pull the battery cable off and put it on and try again

if its the stock radio, the security alarm runs through it, mine did same till i pulled the stock one and put a aftermarket radio in.

It sounds like an inlet manifold seal. Try to rev the engine up to about 1500 revs, if it runs ok, then it's either that or your air-flow mass meter

fuel pump packed in or fuel starvation. check these out first

BMW CUTS OUT
A few things to check.

1. Is fuel pump delivering enough fuel.
2. Is injectors clean. Perhaps dirt in fuel. replace fuel filter
3. Air leakage at top air intake of manifold at ICV idle control valve. Two hoses inside this housing prone to perishing.
4. Throttle position sensor faulty.
5. Mass air flow sensor faulty.
6. ICV faulty or dirty. comon fault on older e36.

Havent done it yet but ICV is easy to clean according to internet. instruction available at bmw e36 blog. All off above can be tested by yourself according to manual.

if you can't hear the fuel pump cut in for a couple of seconds, check the fuse. Check the relay, or replace it with a known good one. See if you have power to the fuel pump. If you have power, your fuel pump is in need of replacement.
When you run an electric fuel pump out of gas, you should always cycle it about 10 times before you try to start the engine. That is, turn the key to on for a few seconds, and then off, and repeat. You need to get some fuel up to the engine.

hi Alex, your symptoms really do point to a failed electrical ignition switch. one possibility is that the dealer gave you the wrong part. there are actually 2 different electrical ignition switches. both will fit. just double check to make sure you have the right one. I would also try, removing the cluster and disconnecting, waiting, and reconnecting the plugs at the back. sometimes the electronics in the cluster can lock up.