Possible Causes
WARNING: This page is about a different car, the 2002 Toyota Celica. However, it is still accessible from the selected car via links, so may be relevant.
DTC 72/B0138 could be caused by a short to battery in Yellow/Black (circuit PL+) and Yellow (circuit PL-) wires in driver-side seat belt pretensioner squib circuit, driver-side seat belt pretensioner squib malfunction or air bag sensor assembly malfunction.
NOTE:
During testing, if DTCs other than DTC 72/B0138 are displayed, disregard them.