DTC DETECTING CONDITION:
Side airbag sensor (LH) is faulty.
When DTC 54 is displayed, the circuit within the side airbag sensor (LH) is faulty.
Replace the side airbag sensor (LH). 
AIRBAG SYSTEM (DIAGNOSTICS) > Diagnostic Chart with Trouble Code
DTC 54 SIDE AIRBAG SENSOR LH FAILURE
DTC DETECTING CONDITION:
Side airbag sensor (LH) is faulty.
When DTC 54 is displayed, the circuit within the side airbag sensor (LH) is faulty.
Replace the side airbag sensor (LH).