A GPS module needs a clear view of the sky and can take several minutes for its first fix. Indoors it often never gets one.
What the message means
The module must hear several satellites. Walls and roofs block the signal. A cold start takes longer than a start with stored data.
Fix it in this order
- Take the module outside, with the antenna facing up and away from metal.
- Wait for several minutes on the first start. The blinking fix LED on many modules shows when a fix is made.
- Connect module TX to your RX pin, and use a hardware serial port if you can.
- Match the baud rate, commonly 9600.
- Power it from a stable supply and join the grounds.
- Check the raw NMEA text on the serial port. If text appears, the wiring is fine and the fix is the problem.
Why it happens
A GPS receiver calculates its position from the signal timing of several satellites. After a cold start it must first collect satellite orbit data, which can take minutes, and then lock onto enough satellites for a position fix. Walls, roofs and metal enclosures weaken or block those signals. Indoors, the module may still output NMEA sentences with empty position fields, so the data stream looks alive while no coordinates are produced.
Separating the causes requires looking at the raw output. If NMEA lines arrive, the wiring and baud rate are correct and only the sky view is missing. If nothing arrives, the fault is in the wiring, the TX to RX connection or the baud rate. Once the raw stream is confirmed, a test outdoors with clear sky is the next step. Many modules blink a status LED when they lock, which gives a visual confirmation without any code.
If you see this, do this
| You see | Do this |
|---|---|
| Text appears, no coordinates | No fix. Go outside and wait. |
| No text at all | Wiring or baud rate. |
Confirm the fix
- Open the raw serial stream at 9600 baud and confirm lines beginning with $GPGGA or $GNGGA appear about once a second.
- In the GGA line, check the fix-quality field: it reads 0 indoors and becomes 1 or higher once the antenna has a clear sky view.
- Move the module outdoors with the antenna facing up, wait several minutes without moving it, then check the fix field again.
Common mistake: Readers assume a receiver with no coordinates is broken, when it has simply not yet collected enough satellite signals to calculate a position.
Related
ESP32 Serial2, serial monitor shows nothing.
Last reviewed: November 2026. These are the usual causes and the order that finds them fastest. Test on your own board; clones and cables differ.