Multitech MMCModem GPRS (MTMMC-G) Reference Manual page 175

Continued: Specific Error Result Codes
<error> Meaning
544 CMUX connection Timeout (no answer from the remote); i.e., no
DLCO opened response.
545 A CMUX session has been started on a physical UART, and the
user tries to start another CMUX session on another physical
UART. The error, +CME ERROR: 545 is raised on the UART
where AT+CMUX command is trying to be started again.
546 Emergency call is not allowed without SIM
547 Emergency call is allowed without SIM
548 No flash objects to delete
549 The phone number of the requested phonebook entry is empty
550 Unable to resize the Application & Data storage place since the
new required size would overlap with the current Open AT®
application storage place
551 Service abort request has failed
552 Unsolicited responses for autodiag or charge indication are
already activated on another port
Multi-Tech Systems, Inc. Wireless GSM/GPRS AT Commands (Document Number S000293I)
Appendix A – Result Codes, Failure Causes, Other Tables
Results from the following commands
+CMUX
+CMUX
+COPS
+COPS
+WOPEN
ATD><index>[;],ATD><phonebook><index>[;]
+WOPEN
AT+WAC
+WDIAG, +WBCM
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