I have a 2002 6.0L engine in my 1995 truck. One project that I'm investigating is building a module to sit on the class 2 serial bus that will display pertinent engine information on a small LCD or VFD mounted in my dash. Information such as change engine oil, reduced power mode, low oil, low coolant, the number of any DTCs present, and some engine data like cooling fan status, transmission temperature, etc. I am considering using the M68HC12 for this since I am already familiar with the HC11 and the HC12 can be had with an onboard J1850 transciever. I was looking through the protocol description and functionality for the GM implementation of the VPW communication protocol and was wondering about how this is implemented in GM's instrument clusters. Is the cluster continually requesting individual PIDs from the PCM, or is the PCM continually broadcasting the data the cluster needs without being requested?
Surely I will have plennnntttyyyy more questions if this project gets off the ground, I'm just trying to assess the viability of even starting this project...