GPS Jamming Detection By MC60 OpenCpu Mode

hi
i work with MC60 OpenCpu

SDK_VER: OpenCPU_GS3_SDK_V1.6

CORE_VER: MC60CAR01A13

For Get Gps Jamming I Set This Command:

char strAT[50];
s32 REET;
Ql_memset(strAT, 0x0, sizeof(strAT));
Ql_sprintf(strAT, “$PMTK838,1*2C\0”);
REET = RIL_GPS_CMD_Send(0, strAT, GPS_JAMMING_STA);

but i dont get any URC…!
What Can I do Please Help Me
Thanks alot