Originally Posted by FireMe

The deployed retractors (when equipped) are not at all noticeable from the outside, but if the rest of the system is repaired then the new RCM will see the deployed retractor and set a code. Unless you had a car like I had a couple of weeks ago that came in from a used car lot. The airbag light came on occasionally and the customer brought it to us to have it looked at. After checking a few things, I found the used car dealership had wired a resistor into the retractor circuit to fool the RCM into thinking the retractor was still live. In fact, it had been deployed. They put the resistor in just to get the airbag light to go off. The car had been in a major wreck, totaled, bought by the used car dealer, and pieced back together and sold. The title was branded, but the customer didn't fully understand what this meant and was not at all happy when it was made clear to him.

The pretensioners, which are part of the buckle, will cause the rubber boot below the buckle to accordion when they deploy. This is somewhat obvious if you look closely. A casual glance may reveal nothing out of the ordinary, as the buckle only shortens a couple of inches.