2004 Vauxhall Vectra engine management system

have encountered several problems i.e.exhaust air mass sensor (air mass sensor replaced) engine management light still came on after driving afew miles had it checked out machine indicated air con problem although air con not in use system reset next time engine management light came on problem detected accelerator sensor
had new sensor fitted drove car seemed o.k then engin management light came on yet again vehicle goes into safe mode every time enginemanagement light comes on turns ignition off waits 5 mins restarts engine am now at wits end as to what else could be wrong getting desperate to find solution as
bought car to tow caravan but frightened to take a chance in case engine management light comes on urgent help required as wife not very happy