Chapter 14 Fault Codes and DescriptionsC2000 Plus 
 
ID*  Display on LCD Keypad  Fault Name  Fault Descriptions 
72 
STO Loss 1 (STL1)  STO1–SCM1 internal loop detection fault 
Action and Reset 
Action condition  Hardware detection 
Action time  Act immediately 
Fault treatment parameter  N/A 
Reset method  Hardware failure, and cannot reset. Cycle the power. 
Reset condition  N/A 
Record  Yes 
Cause  Corrective Actions 
STO1 and SCM1 short circuit lines 
are not connected 
Connect the short circuit line 
Hardware failure 
After you make sure all the wiring is correct, if STOL fault still occurs after cycling
the power, please return to the factory for repair. 
Bad connection of the IO card 
Check if the PIN of IO card is broken. 
Check if the IO card connects to the control board correctly, and if the screws are 
tightened well. 
The IO card does not match the 
version of the control board 
Contact local agent or Delta