quote:Originally posted by PanteraDoug:
So if I am getting your thought on this right, you think the EPS just needs a 12v power source and a way to know how fast the vehicle is moving? That is a "stand alone"?
Wouldn't that make the signal from the VSS necessary and that signal what would be modified somehow with the "dimmer switch", probably with some kind of a mini circuit contained within to 'translate' that signal to a CAN signal if it is not already?
What type of signal does a VSS produce now?
In a sense yes, most modern vehicle modules are just that. They each control their own items and talk to each other via CAN to gain more info. For example an abs module will have four wheel speed sensors. The speed sensors will output either a digital square wave or a sine wave. The abs unit will count these pulses and calculate wheel speed. Rather than trying to connect the four wheel speed sensors to other devices which would have to each do their own calculations the ABS unit merely tells the other modules what the speeds are. As for the EPAS unit it is not quite so simple as a speed input and power. There is a master module in the car which is kind of like a hub. This is usually the BCM or the dash cluster. This module has to first send out a wake up command to all of the other modules to get them ready to receive and send data. After that the modules start to transmit their respective data and receive relevant data from other modules. This is what the Cobalt EPAS is looking for. Without knowing the exact identifier and configuration of the CAN bus data required the EPAS will not be fully functional. For interest sake A can bus message looks something like
000005a1 8 11 22 33 44 55 66 77 88
Imagine a hundred of these flying around the can bus per second. Now imagine trying to figure out which one of those is the one you are looking for. Once you find it you then have to figure out its structure. This is why there aren't a lot of guys out there doing this. Some of the older EPAS units dont use this such as the MR2 units however most if not all of the new ones do.