Engine wont start on my bmw 318 auto

If the dashboard lights on your BMW 318 are not coming on, there could be a few potential causes. Here are some steps you can take to troubleshoot the issue:

1. Check the fuses: Locate the fuse box in your BMW 318 and check the fuse that corresponds to the dashboard lights. If the fuse is blown, replace it with a new one.
2. Check the dimmer switch: The dimmer switch controls the brightness of the dashboard lights. If the switch is turned all the way down, the lights may not be visible. Make sure the switch is turned all the way up.
3. Check the battery: If the battery is weak, it may not be providing enough power to the dashboard lights. Try jump-starting the car or charging the battery to see if this resolves the issue.
4. Check the wiring: If the wiring that connects the dashboard lights to the battery is damaged or loose, the lights may not come on. Check the wiring and make any necessary repairs.
5. Consult a mechanic: If none of these steps solve the issue, it may be a more complicated electrical problem that requires the expertise of a mechanic. A professional mechanic can diagnose and repair the issue to get your dashboard lights working properly again.

check battery

check the cable in the alternator ( the most thick) if gave power with the engine off if don't have power connect a cable from alternator to + battery and check if is working.

Disconnect the battery, have the ignition key turned to the "on" position then reconnect the battery.

Even a relativly new battery can develope a bad or dead cell. Does the engine spin over when ignition is attempted? Easiest way to check this is to load test the battery. Any major auto parts dealer( Advance, Autozone, NAPA, Oriellys,etc.) can test this at no charge. Also use a voltmeter to test the alternator output. Most alternators put out between 13.5-13.8 volts at the battery. A faulty alternator can cause the engines electrical system to pull voltage from the battery until it (Battery)gets down to around 10 volts at which time the voltage is to low to support the needs of the system and the vehicle simply cuts off and will not restart as described in the first part of your post. Hope this helps.

There can be so many issues and unless a code check is confirmed with more inputs from your end including the battery condition, if the engine is cranking or also if the scheduled services were in order.

Try jump starting, see if it starts then. Lights, radio, etc.. don't draw nearly the amps that your starter does. Batteries don't always give warning when then decide to "go south". If you can get it started by jump starting, stop by a local Autozone, Advance, etc.. auto parts store and have them do a charging system test and to load test your battery. They offer this service for FREE
Another Note: When was timing belt last replaced? If it's a 325 of that year it should be done every 60k (If it's 318 ignore the above belt issue)

could be a problem with the security chip in the key.

sounds like you need a new inhibitor switch on the auto

This is not a sloution but i had a similar problem about 6months ago. I left the lights on which drained the battery, road assistant came to booost start it, there was power but no turn over, not even a clunk of the engine trying ( all electrics are working and lights in the dash are live), tried a new battery same situation,
I took it to BMW independant specialist who put it down to a ECU fault , i was duped into having a new key made as i had no spare as it was believed the immobilizer had locked the car up so to speak, this didnt work , so the mech ordered a new ecu, and had it reprogrammed and it turned over first time, It was bumpy idling at cold start cos i had my original dead battery but after a day it ran like it used to sweet as a nut.
it was expensive 500 quid to put right, but then you may have better luck with your mechanic.