For readers who might not understand the wacky key switch inner workings, see the description below. In short, yes the key switch can be eliminated (ignoring issues related to PK3+). Here is how the system is designed to work in a stock Cobalt:
The Body Control Module (BCM) outputs 12v and 5v to to the key switch. The key switch uses these two supply voltages and returns them the BCM in various combinations depending on key switch position. Here is what the BCM expects to see on the three input wires:
- Connector 4 pin C8 - 12v in "Accessory and Run"
- Connector 4 pin D3 - 12v in "Run and Start"
- Connector 2 pin 56:
- 12v in "OFF and Key Inserted"
- 5v in "RUN"
- 5v + resistor in "Start"
There are several ways to replicate this exact setup using switched and or relays. What I have found (only basic testing has been done) on my 2010 SS Turbo is that
the BCM does not seem to care bout the multiplexed signal on connector 2 pin 56. It simply wants to see the ACC and IGN lines powered up with 12v, then it wants to see the ACC line drop out to initiate the start sequence (starter will engage). So, assuming that my simplistic testing is accurate and assuming this applies to more than just my year and trim level, you could use the following schematic as the
most basic way to eliminate the stock key switch:
Please note that the start switch is NORMALLY CLOSED. If using a push button, you may need to use a relay to invert the behavior as most of the fancy "Push To Start" buttons are normally open.
If someone has experience and knows of something that does not work properly when the multiplexed line is not used, let me know. There has to be something, I just have not run into it yet.