TRC VCS & ABS Lights Fault

[astrobhoy]

OK - so the first post of a few I'll be making after buying a rather faulty 2007 D4D! 

The lights for the TRC and VCS seem to come and go quite a lot.  Sometimes I'll start the car and they'll be off and then further into the journey they come on .  Sometimes the lights start on and they stay on - and then also - sometimes the ABS lights come on too!!!   Can anyone suggest what the fault might be here?  I don't have a lot of money to throw at a mechanic to find it and the car is still driving fairly well.

Thanks