Hi, I have a Vectra 2.2 Elite 2003 and the oil light isn't working, I took it to a garage who replaced the oil pressure switch with a genuine GM part but the light still doesn't work (I have the old switch and watched them do the work so it has been replaced). He disconnected the wire from the oil switch and earthed it to the bodywork while the engine was running and the light comes on indicting the light on the dash works. Strangely if he does the same with just the ignition on position two and the engine not running then the light will not come on. It will only light up if the engine is running and the switch wire is earthed. I searched the forum and found one post saying… "The 2002 z22se engine oil pressure warning light will not light up when the ignition is first switched on, it did on the previous year and it will on the 2003 model"... Mine is a 2003 model not a 2002. Can anyone please shed some light on this?

Thank you.