This will be a quick and to the point case study. This 1996 Pontiac Grand Am came to us with the air bag lamp on. First thing I did was went and scanned for codes with my Tech 2. When I tried to retrieve information from the air bag module I got the dreaded message, No Communication.

No communication problems with any module is usually pretty simple to diagnose. The problem will usually either be a power supply issue, ground issue, data line problem, shorted reference voltage issue, or a bad module. First thing I check are the fuses that feed the module that is not responding. If all the fuses are good, I will try to communicate with any other modules in the vehicle. If ok, I will then go directly to the module not communicating and check all of the power supplies and grounds to that module. If there is no problems found there, I will check and make sure the reference voltage is not shorted out. I then also make sure the data line is good back to the dlc and that it is not shorted to power or ground. If I still see no problems, I will check the module connections and then replace the module.

On the this Grand Am, the fuses for the air bag module were good, so my next step took me to the module itself. As with a lot of GM air bag modules, this one was located under the carpet, under the passenger seat. As I was pulling up the carpet, after removing the passenger seat, I was reminded of the 1992 Cadillac Eldorado and it's frozen carpet. The carpet was frozen on this Pontiac as well and there was actually chunks of ice next to the air bag module. Water damage and corrosion were the cause of the no communication problem on this one.

In the pictures you can see the ice chunk, corrosion under the module, and corroded connector and module pins.