Thank you all for your very helpful comments! The part about calling it a spark plug is my bad.
I don't actually have the error code but on the receipt it is marked that injector #4 is not working within specs. It also mentions that the glow plugs need to be replaced. He service guy told me that changing 1 injector would set me back $600 and he recommended that I change all 6 because the problem would spread to the remaining 5??? Is this like a contagious disease?
Anyways I appreciate all the help on this.

What you saying is that if it was a 3.0 V6 Diesel ,then it may need a coilpack..
Yep.....that makes sense.:rofl:

Come on people,BMW doesn't have V6 engines petrol nor diesel.

I was taking the pi** :bustingup:bustingup
Think most of us know that Bmw dont do a V6 ,with the exception of jst2878!:D

Any clues as to what might be going on?

I would go to another dealer because this one is incorrectly advising you to replace all 6 injectors!
This also puts doubts on their analysis that you need glow plugs!
Like I said in my previous post,if you have one or more faulty glow plugs,then you will need to swap all 6,because the fault could spread to any that you havent replaced.
With regards to injectors,you will only need to just replace the faulty one.:)

Thanks for this info. What about labor? Does replacing one injector and 6 glow plugs involve a lot of work?

You have a diesel. It doesn't have spark plugs. You may have a faulty injector but to have five other soon-to-be faulty injectors is highly unlikely at just 74,000km.

Dealer time for replacing those parts ,is:-

GLow plugs (all)...1,50 hours
Injectors (all)......2,60 hours

So if you are going to do it yourself or even an indy,then expect it to take a lot longer!!!

So,quite a lot of work involved and time consuming.Dealer time for removing 1 or 6 injectors is the same!

Thanks powers1, very helpful info indeed!
Scheduled an appointment to replace the injector in about two weeks time. Dealer told me that I should be able to drive normally until then, is that correct? Could I be in for some nasty surprise like totaling the engine if I drive with one malfunctioning injector?