You need a scan tool and a multimeter to perform the tests to diagnose the problem. There are some items you can check though
The pictures in this super long post may not come thru. If not and this is a job you would like to tackle then I will enter them manually.
PID/Data Monitor and Record
Battery Ground Cable
Power Distribution Box Fuse 2 (10 A)
Air Bag Diagnostic Monitor C208 and C209
Retrieve/Clear Continuous DTCs
Pinpoint Test B: LFC 13/53/DTC B1913 - Air Bag Circuit Shorted to Ground
The air bag diagnostic monitor measures the voltage of the air bag modules at Pins C209-2, C209-3, C209-4 and C209-5. The voltage at these pins is set by the air bag diagnostic monitor and varies with the charging system voltage. If the air bag diagnostic monitor detects low voltage on any of these pins, it will store a diagnostic trouble code (DTC) B1913 in memory and flash a lamp fault code (LFC) 13 on the air bag indicator to indicate a possible short to ground on these circuits.
At the same time the air bag diagnostic monitor begins flashing LFC 13, it attempts to disarm the air bag supplemental restraint system (SRS) by activating an internal solid state switch at Pin C209-13, Circuit 937 (R/W). The activation of this switch shorts Circuit 937 (R/W) to ground, causing the power distribution box Fuse 2 (10 A) to open, disarming the SRS and preventing inadvertent air bag deployment.
The air bag diagnostic monitor will make up to three attempts spaced one minute apart to blow the power distribution box Fuse 2 (10 A).
If the attempt to blow the fuse is successful, a DTC B1867 will be stored in memory.
If the attempts to blow the fuse are unsuccessful, a DTC B1924 will be stored in memory.
After the power distribution box Fuse 2 (10 A) has been blown or three attempts to blow it have failed, the air bag diagnostic monitor will not attempt to disarm the SRS again until DTC B1913 has been repaired and cleared from memory.
Should the low voltage or short to ground on these pins be intermittent or repaired, the air bag diagnostic monitor will flash an LFC 53 (or a higher priority LFC such as LFC 12 if one exists) on the next ignition switch cycle.
WARNING: Repair of lamp fault code (lfc) 13/diagnostic trouble code (dtc) b1913 will usually occur after the repair of lfc 12/dtc b1867 has been completed. Do not under any circumstances substitute another fuse value for the power distribution box fuse 2 (10 a). Any fuse other than 10 a can cause disarming failure and can result in danger to the occupants of the vehicle. Do not attempt to replace the power distribution box fuse 2 (10 a) unless the battery ground cable has been disconnected and the backup power supply energy has been depleted. To deplete the backup power supply energy, disconnect the battery ground cable and wait one minute. Be sure to disconnect auxiliary batteries and power supplies (if so equipped).
Low voltage at air bag diagnostic monitor Pins C209-2, C209-3, C209-4 or C209-5 can be caused by:
I figured they would not come thru.