Pontiac Problems? Ask a Mechanic for Answers ASAP
Here is the starting system electrical diagram. Please let me know if I can assist further.
Since you are dealing with computers in this circuit, you will not have 12 volts on these wires. The Black/White wire should have 5 volts with the key on, and should go to 0 volts with the key turned to the start position.
Does the voltage change at all when the key is turned to start?
Not a significant change then. Do you show good continuity to ground on the White wire at the ignition switch connector? If so then it would appear that the ignition switch is faulty. Of course the best way to test would be with an advanced scan tool that you could read data from the BCM showing what state the ignition switch is in (off, on, start).
Have you already replaced the ignition switch?
Recheck the white wire voltage. You stated you are getting 12 volts on this wire, it should show no more than 5 volts.
What is voltage on white wire in START position?
Sounds like the ignition switch is working okay with voltages changing in each different position of the switch. If the data does not display correctly then the problem is likely in the BCM. This could also be the reason the high beam indicator is coming on sometimes.