These Vectras did suffer with crankshaft and camshaft sensors but I think more likely it is the idle speed control valve or possibly the airflow sensor.
The Idle valve should be located near the top of the inlet manifold close to the rocker cover and the Air flow sensor would be between the air filter box and inlet manifold.
You can try cleaning out the Idle valve with brake cleaner for a temporary fix but don't use it on the air flow sensor. If the engine light is coming on, take it to a garage with a diagnostic machine where they can tell you exactly what the problem is for about £15 to £30ish. Also should cover the ABS too. sounds like they may have knocked off a wire or pick up on the hub. Hope that helps.
Will Brown, January 2009
