Thanks for the replies. Just a thought if the glow plug control module was faulty then wouldn't I be also reading the fault code '4203' for the glow module? 

[quote="Horizon"] Sounds like a vacuum leak or the EGR valve is sticking open, easy enough to remove and clean with carb cleaner, search the forum there is a few posts. Glow plug sounds like the module, but is worth testing each plug as mentioned as they are a common failure. Oil wear transmission ...

Thanks for everyones reply. Managed to get the car onto a diagnostics machine today and it came up with the following codes: 4530 - Charge-air pressure control 4501 - Exhaust-gas re circulation It also had fault codes for every single glow plug: 4212 - Glow Plug, Cylinder 1 4222 4232 4242 4252 4262 ...

I've just purchased a 2003 (facelift) E53 X5 which I am loving at the moment but I have a few niggles that hopefully can get some advice on? 1. The engine temperature gauge doesnt go past the cold indication. I thought it might be a fault gauge but there is not much hot air being blown out the vents ...