Is 220d car won't start (immobilizer lock out)

[Flyman1]

Hey guys (sorry for my poor up to come Grammer)

So I have my 2007 is 220d and I've been having issues .I've been driving the car normally but if I want to start the car a 2nd/3rd time after a couple of hours ,it won't start .

The dash will say key not detected .which  is weird because I can open the car with the electric key and unlock it but the immobilizer kicks in as soon as I try to start it . I have the original key and a spare which I programmed myself .

I have a expensive diagnostics tablet .it comes up with no faults ...wtf . 

So I've narrowed down the problem to a computer module that is potentially over heating .( when car is on, not engine ).

Will update and let people know what the problem was. if anyone has had this problem please let me know .

Thank you in advance 

[madasahatter]

Is250s go through batteries like nothing on earth. Have you tried a new Battery in the fob? I personally carry a spare in the car.

[Flyman1]

A the thing is I have like 3 spare batteries for the fob  and last time I changed it was like 3 weeks ago ...I changed the Battery in it when the car didn't want to start and still nothing

[Linas.P]

My immobiliser stopped working after driving car to carwash and petrol station, haven't worked since November...

Not sure if the issue can be related, which computer you think is overheating? 

[Flyman1]

Haven't got the parts yet but I'll be replacing ,most of them one by one and then I'll run through with the diagnostics tablet and a voltmeter