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Dave Nova
Dave Nova, Pontiac Technician
Category: Pontiac
Satisfied Customers: 19452
Experience:  ASE Master Certification. GM World Class Certification
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08 G5 no crank, no power coming from ignition switch to

Customer Question

08 G5 no crank, no power coming from ignition switch to crank relay. Looking for wiring diagram of ignition switch
Submitted: 2 years ago.
Category: Pontiac
Expert:  Dave Nova replied 2 years ago.

Here is the starting system electrical diagram. Please let me know if I can assist further.


Customer: replied 2 years ago.
Ok I have no power in wh/bl wire or white wire with key in start position. Going to install new ignition switch.
Customer: replied 2 years ago.
I have 12 volts coming to switch on red wire and 12 volts going out on brown wire and yellow wire. Got nothing on wh/bl and white wires. Do I only have one feed to my ignition switch?
Expert:  Dave Nova replied 2 years ago.

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.

Customer: replied 2 years ago.
Got 5 volts on Wh/bl wire but it does not drop to zero in start position.
Expert:  Dave Nova replied 2 years ago.

Does the voltage change at all when the key is turned to start?

Customer: replied 2 years ago.
Wh/bl wire has 5 volts key off, 3.9 volts with key on and goes to 4.2 volts in start position. Battery is at 12.4 volts.
Expert:  Dave Nova replied 2 years ago.

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).

Customer: replied 2 years ago.
I have ground showing on white wire till I put the key in (not turn key just put it in) then it shows 12 volts on white wire. I have a snap-on Modis scanner here at our shop.
Customer: replied 2 years ago.
Scanner says no for key in the ignition when the key is in and turned on.
Expert:  Dave Nova replied 2 years ago.

Have you already replaced the ignition switch?

Customer: replied 2 years ago.
it made no difference.
Expert:  Dave Nova replied 2 years ago.

Recheck the white wire voltage. You stated you are getting 12 volts on this wire, it should show no more than 5 volts.

Customer: replied 1 year ago.
Rechecked white wire using a power probe, shows ground with key off and out of ignition, shows battery voltage when I put key into ignition, shows 3.9 volts when I turn key on
Expert:  Dave Nova replied 1 year ago.

What is voltage on white wire in START position?

Customer: replied 1 year ago.
Drops to 2.9 in start position. Also I am noticing that the bright lights indicated (red light) comes on when I cycle the ignition switch and stays on till I turn headlights off and on? It does not do it every time just some times.
Expert:  Dave Nova replied 1 year ago.

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.