Airbag Light | 1996 Pontiac Grand Am | No Communication
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.
3 comments
Good, logical approach! No communication issues are often followed by lots of guessing, rather than standing back and considering the possibilities. How does the thing work? If you don’t know how; don’t guess, or start out on a parts shopping spree. Identify the all the components; understand their function; how they interrelate, and how they could, do, or don’t contribute to the problem. Every wire has two ends. Dynamic testing beats static testing. And volts drops find high resistances, which on modern véhicules are less and less tolerated by control units; giving rise to countless problems, which are often not shown by static tests. Resistance testing alone is futile in circuit wiring tests as it doesn’t prove that the circuit can carry the load required to operate the consumer: only that the circuit is complete – or not! Understand; consider; test; confirm – and do clear codes where appropriate, when finished!!
Your articles are much appreciated. We’ve all struggled in our quest to find a problem, but it’s clear that understanding the workings, and following the basic rules is the only way to go!
I have the same car with the same problem. My question is this. If I replace the module myself with one from a car that has nt been wrecked is there any chance of it wrking without having to be reprogrammed frm the dealership?
It will need to be programmed and a new BCM may also be needed to successfully program it (normally 2000′s and up).