Onstar

Every summer, I become obsessed with building a new show car. I'm ready to sell the Escalade, the Panasonic Stealth is making its tour of the continent and the Honda is complete. My big question is, "What next?" I love the new Challenger, but it won't be out for a few years. The BMW Mini has been done a million times. I want to build something in time for the SEMA show in late October, but I can't decide on a platform. I would love to hear your suggestions for a new build-send your ideas to dereklee@mobiledynamics.com and you might see your suggestion in the pages of Car Audio and Electronics...

Q| First off, I would like to say that your column is the first thing I flip to when I get my monthly Car Audio mag. You have helped me many times and taught me so much. One of the things I have yet to see you go over is installing an aftermarket head unit into a car with OnStar. I have 2001 Suburban. The factory unit was not equpped with RDS (Radio Data System) and I do not have the Bose system. I bought a Pioneer Premier DEH-P860MP head unit and a Peripheral interface. I do not know the model number, but I was told it was the correct one to keep my OnStar working. After the shop did the install, they could not get the OnStar to work. The head unit works fine, but the OnStar doesn't even light up. The shop said they called a couple places for help (who, I don't know) and tried two interfaces. Still they can't figure out how to get it to work. The best they can do is getting the OnStar to light up for a couple seconds when it is first plugged in. Please help me-I hate having something that doesn't work.Thanks,James

A| With the variety of factory electrical systems and aftermarket interface adapters, there is as much complexity in connecting an aftermarket head unit as there is in adding some type of card to your PC. The product exists, but there are always little init files, configuration files or even hardware mods that leave you scratching your head while your PC exhibits unusual behavior. GM's Class 2 serial data bus, and the many software anomalies it seems to have, prompted me to call the software in GM cars "Windows."

Since Peripheral offers a large number of interfaces, there should be no problem getting this to work. Without knowing which model of interface you have, I can't get specific. Unfortunately, troubleshooting an interface on the Class 2 bus requires more than just a DMM (digital multimeter) if you want to get to the actual code structure of the commands. If your install shop contacted tech support and other sources of information without luck, my guess is that there is an "issue" with the vehicle that is causing it to fight the interface.

Since the OnStar lights up briefly, it is likely receiving a proper command. That it shuts off leads me to believe that either the interface is sending a second incorrect command or the OnStar system is responding incorrectly. When that happens, and I have confirmed it is not a faulty interface or connection, I will often shift to another brand of interface adapter to confirm if the vehicle and product application are workable. In the rare instances when I suspect the interface and OnStar are fighting, this solution works. It doesn't answer the why question, but with a customer waiting to leave, I just want some results...