A common method of easily checking that a GPS module is outputting serial data is the serial passthrough which displays on the serial monitor each byte available in the serial buffer:
while (Serial.available()) Serial.write(Serial.read()); //displays ASCII characters
Another method is to use the serial plotter to trace the status of the GPS TX pin:
Serial.println(digitalRead(receivingPin)); //plots 1 or 0
Maybe the plotter method is just a curiosity but I think it's of interest and instructive.
The sketch:
/*GPS pass thru two ways;
uses one of two methods:
1. traces status of GPS TX pin on serial plotter
or
2. displays GPS output on serial monitor as ACSII sentences
*/
const int receivingPin = 0; // GPS TX connected to this digital pin
void setup() {
// initialize the receiving pin as input:
pinMode(receivingPin, INPUT);
// initialize serial communication:
Serial.begin(9600);
}
void loop() {
//comment out the method you do NOT want to use
//use this method to trace status of GPS TX pin on plotter
Serial.println(digitalRead(receivingPin)); //plots 1 or 0
//use this method to display GPS sentences on monitor
while (Serial.available()) Serial.write(Serial.read());
}