drivers side seat belt tensioner open

Ed, The seat belt buckle switch can be tested using an ohm meter. Disconnected the switch and measure the circuit. If it shows open then the seat belt buckle will need to replace. You can verify this with a 2.5 ohm resister installed in place of the seat belt buckle. If the buckle does not test open you can use the same resister to test the air bag control module by installing the resister in line at the air bag module connector. As always following the safety guidelines for disarming the air bag system first