Headlight goes off and comes back on sometimes straight away sometimes it takes 30seconds or longer, if i switch them off and back on they come on again, this is happening with both lights but not at the same time

Looks like the multi function switch goes to the cluster where lighting commands are issued across the CAN to the TIPM.

What codes are stored?

If there are CAN bus failures then there's what to go after first. Otherwise it's likely a failing TIPM, but all the TIPM and instrument cluster power and grounds need to be checked.

Alternators can sometimes whine when start up on a cold morning, they run on full load till they get the battery back up to full charge. When the whining stops, switch on electrical equipment (Headlights, fan full boost, heated rear window) if the whining starts again its the alternator.

if you have alot things on keychain ignition could be going bad. shake switch when it happens. sometimes remove weight from keys can stop it

you have a bad headlight switch

On the top of the radiator support above each headlight there are 2 pins that are locked in to place that can simply be rotated and pulled straight up and they come all the way out they both the same size about 6 inches long. Once you pull them out the whole headlight assy is now loose and can be pulled away from the body allowing you to access the bulbs. Changeing both should take no longer than 5 minutes. Once you figure it out it's a smoke

did you check the coolant sensor and see what it is reading ?

You have to remove the panel to check onthe connections behind it, also check the headlights switch, they tend to burn out.

I had the exact same problem, I changed the "ignition switch" because the contacts inside were burned, this is why you see all those troubles coming in and out at different moments. It costed me 150$ to do it myself, buy the switch on an online reseller, must cheaper than the dealer! Now everything is back to normal on my Grand Prix GT 99 exept that my headlights don't light up automatically when starting the car... I have to check my fuse/relay and switch to make sure everything is ok on that side.

Good luck.

The multi function switch is the turn signal switch. It also does control wipers and lighting. If you are having the issues you describe then you will most likely have a body control module problem. Before you spend the money to buy the module and get it programed get it checked first. Goot Luck

try replacing both headlights. sometimes if one goes bad they both wont work