GSM not responding to AT commands - arduino

Question

I am using GSM 900A modem which requires 5V Supply. I am connecting it to Arduino UNO. I am giving supply to modem by arduino 5V and GND pin. I am connecting RXD pin to TX(pin 1) of arduino TXD pin to RX(pin 0) of arduino and GND to GND of arduino i.e. pin 14. I am running the basic example codes but GSM is not responding. I have also tried other softwares like Putty but I am unable to write any AT command Please help me. When I tested the modem using this code:
/*
This example tests to see if the modem of the
GSM shield is working correctly. You do not need
a SIM card for this example.
Circuit:
* GSM shield attached
Created 12 Jun 2012
by David del Peral
modified 21 Nov 2012
by Tom Igoe
http://www.arduino.cc/en/Tutorial/GSMToolsTestModem
This sample code is part of the public domain
*/
// libraries
#include <GSM.h>
// modem verification object
GSMModem modem;
// IMEI variable
String IMEI = "";
void setup() {
// initialize serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for Leonardo only
}
// start modem test (reset and check response)
Serial.print("Starting modem test...");
if (modem.begin()) {
Serial.println("modem.begin() succeeded");
} else {
Serial.println("ERROR, no modem answer.");
}
}
void loop() {
// get modem IMEI
Serial.print("Checking IMEI...");
IMEI = modem.getIMEI();
// check IMEI response
if (IMEI != NULL) {
// show IMEI in serial monitor
Serial.println("Modem's IMEI: " + IMEI);
// reset modem to check booting:
Serial.print("Resetting modem...");
modem.begin();
// get and check IMEI one more time
if (modem.getIMEI() != NULL) {
Serial.println("Modem is functoning properly");
} else {
Serial.println("Error: getIMEI() failed after modem.begin()");
}
} else {
Serial.println("Error: Could not get IMEI");
}
// do nothing:
while (true);
}
I am getting this output on Serial Monitor for 9600 baud rate:
Starting modem test...ERROR, no modem answer. Checking IMEI...Modem's IMEI: 0 Resetting modem...Modem is functioning properly

Answer 1

I think it has to do with your supply, try using an adapter, that outputs a current of 500mA to 1A.