What is the manu. year and engine capacity Tony?
Are you able to read the trouble codes? At the back of the engine bay (iirc RHS) there may be two diagnostic units (only on certain age models though). If so, on diagnostic box A plug flylead to posn 3. Turn ign on. Press and hold the button on diag box for 1sec. The fault sequence will return as a sequence of flashes on the diagnostic unit LED separated by a few seconds gap, i.e. two flashes, gap, three flashes, gap, two flashes = 232. Press the button again for next trouble code.