hi,guys,my laguna has developed a problem engine managment lihgt came on and talking computer says ,anti pollution monitor faulty,intermitten when starting sometimes it starts first turn,next time turns for ages before catching,when in for mot last wk, asked guy to put on diognostic,came up with,flywheel speed sensor fault,he reset it all fine for day or so no dash light,then dash light came back on same problem back,does anyone know where it it and what to do have looked in manual cant find any refference,to where it is or how to fix,much appreciate any help,thanks