My BMW X1 S DRIVE 18i, 2012 will not start despite all diognostics being done and keys and battery fully charged.  Started with engine service light staying on then it just refused to start. My mechanic has 3 other identical BMW's with the identical problem and BMW dealer cannot help.

Morning Michael

Welcome to the Forum

First you say a Diagnostic has been run? Using which diagnostic equipment? A general OBD scanner or out of date BMW system will not be capable of seeing individual control units. A scan with an up-to-date BMW capable Diagnostic program may show more.

You say the Battery is fully charged, I hope that when it was charged it was at the charging points under the bonnet or disconnected before charging if done at the battery. If the battery was connected to the car and a charger/booster attached there could be damage to several control units.

The fact your mechanic has 3 other cars with the same problem would worry me. The Dealer cannot help or will not help? That again is a worry for me normally they can't wait to take your money.

So, to your problem First principles of combustion 4 things are needed Compression, Fuel, Air and Ignition

I would start with a compression test, assuming all is OK the next test is Fuel. Is there fuel at each injector has their harness been checked, what is the fuel rail pressure? Is it correct if it is OK if not check Fuel Pumps Filter and fuel rail sensors and fuel lines for blockages. Air MAF checked and tested Air Filter OK no leaks on the Induction side? Ignition, are all plugs in good condition and correct for the car, are all ignition coils tested and working, has the loom been tested and checked. Finally, timing has that been checked are cam and crank sensors OK and tested? Are the engine earth straps in good order.

If the above is OK then time for a full Diagnostic scan. Attention should be paid to any Control Unit that is greyed out or not accessible. You could have an issue with the stop/start button, gearshift switch a relay or fuse.

BMW Diagnostic Equipment needs to be up to date As an example BMW 1.4.0 will read vehicles up to 2005/6 when the Bus system was updated, from then on you need INPA which will read all models up to around 2012/13 after that date ISTA is needed all these programs are backwards compatible. There are now some BMW capable systems from Carly, Foxwell and Icarsoft. The advantage with BMW programs such as INPA/ISTA is they have WIS (workshop Information systems) and TIS (technical information systems) built in

Bit of a ramble but I hope it helps

Dave