i had the same fault in my car.open the round multi-plug on top right hand side of the engine and check for corrosion on the pin connectors. if you have green discolouration on pins this could be the source of your problem.im having the engine wiring loom changed in my car later this week, i,ll let you know if it cures it. If you find discolouration on your pins spray contact cleaner into both sides of the plug and open and close the plug repeatedly and hopefully this should inprove connections