You need to scan the system for codes and proceed from there. If the truck has a seatbelt pretensioner it likely blew and is setting a code. Or the system just needs to be reset with a scan tool. Or the module itself needs to be replaced or there are services on Ebay that reprogram them. https://www.ebay.com/itm/FITS-FORD-SRS-AIRBAG-COMPUTER-CONTROL-COMPUTER-ECU-RCM-SDM-ACM-MODULE-RESET-3S-T/183551496394?fits=Model%3ARanger%7CMake%3AFord&hash=item2abc8590ca:g:pfwAAOSwDElb024z