Hello,

I am involved in a CAN bus application. It is not restricted to Chevy vehicles, but obviously they are a large company so it would be nice for my application to work with Chevy vehicles as well.

I suppose I have three questions:

1. What kinds of messages does Chevy send over CAN bus? I understand that all cars since 2008 have been required to implement OBD-II on CAN bus, but how about normal messages like "roll window up", or "turn stereo volume down"? Are these messages accessible from the standard 16-pin OBD-II connector? Does Chevy use GMLAN?

2. How would one decipher these messages? Chevy must have documentation for how these messages are encoded (i.e. the 11 or 29 bit ARB ID used by CAN bus), but I would imagine this information is heavily guarded. Who would one contact to find this information?

3. Do any Chevy vehicles carry a feature sometimes called "automatic air recirculation"? In a nutshell a pollution sensor is placed in the path of the fresh air intake, after a filter perhaps. When the pollutant (NOx, CO) level reaches a certain height, the sensor triggers the car into recirculation mode to prevent the pollutants from entering the cabin.

Thanks,

Chris