HDC failure after head gasket replaced

Hi, got the car sorted. New HG and got it skimmed at same time. This cured problem but gave me a new one. The HDC warning light has now come on. Was working ok up till garage did head. Been back on the Diagnostics at the garage but not showing up any faults. The mechanic says he does not know what else to check unless I can give him some pointers. So can anyone shed a bit of light on this. Is it a common fault and is there a common cure. Any suggestions appreciated
cheers Rock
BTW for those who do not know its a 1.8 Petrol Freelander 51 plate

About the only thing that doing a HG that would affect HDC is the throttle cable,just make sure there is plenty of free play on it.

eightinavee said:

About the only thing that doing a HG that would affect HDC is the throttle cable,just make sure there is plenty of free play on it.

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If tightening this cable. .would that screw the head gasket ? Cause I made mine quite tight.

Had it back at the mechanic today to chech free play in throttle. He says there is free play there but does not know how much there should be. I am based in spain now and this garage is not the one (obviously) I have been using over the 5 years I have had the freelander. He asked me to try to find out any technical specifications I could on the HDC. I did a search and ploughed through some of the threads but found nothing specific.
Can someone tell me how much free play throttle cable should have in engine compartment?
What is the significance of the accelerator pedal in relation to this?
What should the idle speed be?(get a judder now & then when accelerating)
Finally since HDC was working before HG was replaced is there any chance it just packed in or is it related to the relacement of the gasket?
Again, sorry about the infrequent replies but I have no Internet at home and have to travel to nearest town to cybercafe.
Cheers Rock