Garmin sonar modules have a status light on them that provides insight into the operation of the sonar module and shows when errors have occurred. This status light can be red, green, or orange, and will generally flash or blink.
Update the chartplotter and sonar module's software during the initial installation. See for more information.
Click the sonar module below to view the status lights and related troubleshooting steps:
GSD™ 20 sonar module | GSD™ 21 sonar module | GSD™ 22 sonar module
| Light Behavior | Meaning |
 | Green blinking, on for 1 second, off for 1/2 second (slow blink) | The sonar module is wired to a single chartplotter and is operating correctly. The connected chartplotter should display sonar information. |
 | Green blinking, on for 1/2 second, off for 1/4 seconds (fast blink) | The GSD 20 sonar module is wired to two chartplotters and is operating correctly. The connected chartplotters should display sonar information. |
 | Green solid light | The sonar module has experienced a hardware failure—contact Product Support for assistance. |
 | Red blinking, on for 1 second, off for 1/2 second (slow blink) | The sonar module is turned on but does not detect any chartplotter connection. Verify the connection of the module to the chartplotter, if code persists, check the Marine Network connections and verify all system software is up to date. |
 | Red blinking, on for 1/10 second, off for 1/10 second (very fast blink) | System error. The chartplotter displays a message indicating the type of failure. Correct the source of the error, then the sonar module must be completely disconnected and reconnected to the power source to clear the error. |
 | Red solid light | Sonar software failure. The chartplotter may display an error message. Power must be cycled on both the chartplotter and the sonar module to clear the error. It is recommended to . |
 | No light (turned off) | The sonar module is receiving no or insufficient power from the power/data cable on the GSD 20 and 21, or the marine network cable on the GSD 22. |
GSD™ 24 sonar module |GSD™ 25 sonar module | GSD™ 26 sonar module | GSD™ 28 sonar module
| Light Behavior | Meaning |
| Green blinking, on for 1 second, off for 0.5 seconds (slow blink) | The sonar module is operating correctly. The connected chartplotter should display sonar information. |
| Red blinking, on for 1 second, off for 0.5 seconds (slow blink) | The sonar module is turned on, but does not detect any chartplotter connection, or has a malfunctioning XID that changes the transducer's frequency settings. Verify the connection of the module to the chartplotter, if code persists, check the Marine Network connections and verify all system software is up to date. |
| Red blinking, on for 1/10 second, off for 1/10 second (very fast blink) | System error. The chartplotter displays a message indicating the type of failure. Correct the source of the error, then the sonar module must be completely disconnected and reconnected to the power source to clear the error. |
| Red solid light | The sonar module has experienced a hardware failure—contact Product Support for assistance. |
 | Red and green blinking, alternating (fast) | The sonar module is in test mode. Ensure that the network cables are correctly connected, and the system software is up to date. |
| No light (turned off) | The sonar module is receiving no or insufficient power from the marine network cable or the power cable. Check the network cable and power cable to make sure it is functional and properly installed. |
GCV™ 10 sonar module
| Light Behavior | Meaning |
| Green blinking | The sonar module is operating correctly. The connected chartplotter should display sonar information. |
| Red blinking, on for 1 second, off for 0.5 seconds (slow blink) | The sonar module is turned on but does not detect any chartplotter connection. Verify the connection of the module to the chartplotter, if code persists, check the Marine Network connections and verify all system software is up to date. |
| Red blinking, on for 1/10 second, off for 1/10 second (very fast blink) | System error. The chartplotter displays a message indicating the type of failure. Correct the source of the error, then the sonar module must be completely disconnected and reconnected to the power source to clear the error. |
 | Red and green blinking, alternating | The sonar module is in test mode. Ensure that the network cables are correctly connected, and the system software is up to date. |
| No light (turned off) | The sonar module is receiving no or insufficient power from the marine network cable. Check the network cable to make sure it is functional and properly installed. |
GCV™ 20 sonar module
| Light Behavior | Meaning |
| Green, blinking | The sonar module is operating correctly. The connected chartplotter should display sonar information. |
| Red, on for 1 second, off for 0.5 seconds (slow blink) | The sonar module is turned on but does not detect any chartplotter connection. Verify the connection of the module to the chartplotter, if code persists, check the Marine Network connections and verify all system software is up to date. |
| Red (rapid blink sequence) | System error. The chartplotter displays a message indicating the type of failure. Correct the source of the error, then the sonar module must be completely disconnected and reconnected to the power source to clear the error. |
| Red and green blinking, alternating (slow) | The sonar module is in test mode. Ensure that the network cables are correctly connected, and the system software is up to date. |
| No light (turned off) | The sonar module is receiving no or insufficient power from the marine network cable. Check the network cable to make sure it is functional and properly installed.
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GLS™ 10 sonar module
| Light Behavior | Meaning |
| Green, blinking | The sonar module is operating correctly. The connected chartplotter should display sonar information. |
| Red, blinking | The sonar module is turned on but does not detect any chartplotter connection. Verify the connection of the module to the chartplotter, if code persists, check the Marine Network connections and verify all system software is up to date. |
 | Orange, blinking | A software update is in progress. |
 | Red, two blinks followed by a 3-second pause | Other type of sonar failure. |
 | Red, three blinks followed by a 3-second pause | The sonar module does not detect the transducer. If this code persists, check the wiring connections. |
 | Red, five blinks followed by a 3-second pause | The sonar module input voltage exceeds the maximum input voltage. |
| No light (turned off) | The sonar module is receiving no or insufficient power. Check the power cable and power source to make sure the wire and the source are functional and properly installed. |