arduino yun and gsm shield

Hi to all, i have a arduino yun and i have this shield gsm http://arduino.cc/en/Main/ArduinoGSMShield
i read this guide http://arduino.cc/en/Guide/GSMShieldLeonardoMega
and i us e this library http://arduinoshield.tid.es/GSMLibrary/GSM3.zip but
when i use this sketch for test the modem http://arduino.cc/en/Tutorial/GSMToolsTestModem
but i have this error

Starting modem test...ERROR, no modem answer.
Checking IMEI...Modem's IMEI: 0
Resetting modem...Modem is functoning properly

can you help me?
best regards
J.

Plz can u give me solution of this problem...

Im using SIM900A when i upload code-GSM/test modem, Having Error-

Starting modem test...ERROR, no modem answer.
Checking IMEI...Modem's IMEI: 0
Resetting modem...Modem is functoning properly

@Nikhatm,
This post is almost one 1 year old. Please start a new post explain your problem again.

Jesse