Ford 2003 Mustang Workshop Manual page 4060

Is the resistance less than 10,000 ohms?
L3 CHECK THE AIR BAG TONE WARNING INDICATOR MODULE
CIRCUIT
Measure the resistance between RCM C2041 pin 26, circuit 1083
(LB/BK), harness side and GEM C201e pin 10, circuit 1083 (LB/BK),
harness side.
Is the resistance greater than 10 ohms?
L4 CHECK THE AIR BAG TONE WARNING INDICATOR
Disconnect: GEM C201e.
Key in ON position.
Measure the voltage between RCM C2041 pin 26, circuit 1083
(LB/BK), harness side and ground.
Yes
REPAIR the
circuit. GO to L6 .
No
GO to L4 .
Yes
INSTALL a new
GEM. GO to L6 .
No
INSTALL a new
RCM. GO to L6 .