My 1994 Mercury Grand Marquis Airbag light is flashing in a sequense of one flash followed by five flashes. What is this telling me?

There is no code 15 but there was a popular code 51 for the internal fuse being blown and the short to ground no longer being present. If the short to ground returns the code will change to 13 (air bag circuit shorted to ground) or 14 (primary crash sensor circuit shorted to ground) but it will only flash 13 or 14 when the short is present. If it is code 51, then first find and repair the short before replacing the diagnostic monitor (what many call the air bag module).

If you're positive the code is 15, then the only possibility is the alternative reference which makes it the equivalent to C1414 of the modern system which is for incorrect module configuration. Earlier diagnostic monitors use a combinations of powers, grounds, and open circuits at three specific pins to determine if it is in the correct vehicle. If that's the case, a wiring issue could be the cause.

Has anything been altered or does the vehicle have any aftermarket accessories installed that could have compromised the wiring harness integrity?