A vehicle's airbag warning light flashes immediately after starting, and a scan tool retrieves a code for high resistance in the driver's side airbag circuit. Which diagnostic step should be taken to isolate the fault?

1. Replace the passenger side seat occupancy sensor first
2. Disconnect the airbag module, install a dummy simulator resistor, and check if the circuit code status changes to active or stored
3. Connect a jumper wire across the battery terminals with the key in the ignition
4. Adjust the engine idle speed using a scan tool to increase alternator output voltage