Possible Causes
WARNING: This page is about a different car, the 1996 Ford Probe. However, it is still accessible from the selected car via links, so may be relevant.
Code 13 will set if a short to ground is present in circuits No. 931 (Brown/Black wire), 932 (Brown/Red wire), 933 (Brown/Green wire), 937 (Gray wire), 938 (Red wire), 939 (Green/Red wire), 944, 944A, 944B, or 944D (Green/White wire). Code 13 will also set if clockspring is shorted to ground, safing sensor is shorted to ground internally, one or more impact sensors are shorted to ground or air bag is shorted to ground internally.