On the GTA that light is often sensor related, example being the coolant temp feed to the ECU being out of range. If it's flashing it's often the actual connector as opposed to the sensor that's at fault.
Worth unplugging a few and giving them a squirt of Servisol, wipe clean, dry and re-connect. Some people zip-tie the connectors together to ensure a better contact.
Also another top tip, open the engine bay at night (in the dark with the car running) and look closely along the HT leads. You shouldn't see anything. If you can see blue arcing then the insulation is breaking down so best replace.
Dizzy cap is another potential suspect but you've done that right?
I'm just here for the gasoline.