2003 Buick Century security system. When the ambient temperature goes above 90 the security system is set, even with a cold engine. Below that, everything works properly.

More details. Car in the driveway, thermometer in the car. Started the car every two hours, no problems. Temps up to 120. The last check was after dark, temp down to 90: No start. Left the key in "ON" position with security light blinking. Wait 2 - 3 minutes until light is on steady. Turn key to off, then start. Yay, it works. Same thing twice today, car temps at 100 and 90. Will bypass the ignition switch sensor with a resistor, per internet. If this confirms a bad switch we will replace it. Would it really help to have the system scanned?

Dealer scan gave us a B2958 code. I also did the resistor bypass and the car starts & runs without any security light. An AC Delco ignition lock cylinder has been ordered so we can reset it to match existing keys. I have the key resistance and VAT number, but resetting the lock is cheaper.