Leica ERR-004 Error: What It Means and How to Fix It

Applies to: Leica GS18, GS15, GS10, GS14 GNSS rovers

What Does ERR-004 Mean?

ERR-004 Bluetooth Lost on Leica GNSS receivers indicates the Bluetooth radio link between the receiver and the Leica CS35, CS10, or other paired field controller has dropped. The receiver continues to track satellites and receive RTK corrections but cannot transfer position data to the field software until Bluetooth is restored.

Leica GNSS rover and field controller pairs communicate primarily via Bluetooth at close range (typically 0-30 meters). When the controller and receiver are carried by the same operator, this connection is normally reliable. ERR-004 appears when the controller and receiver are out of Bluetooth range, when physical obstruction interrupts the signal, or when a Bluetooth firmware issue causes the connection to drop.

Common Causes of ERR-004

• Field controller moved out of Bluetooth range — typically beyond 20-30 meters from the receiver
• Physical obstruction between controller and receiver blocking Bluetooth signal
• Bluetooth interference from other devices nearby (other survey equipment, smartphones, tablets)
• Field controller Bluetooth turned off or went to sleep to conserve battery
• Bluetooth pairing tables corrupted — requires re-pairing
• Firmware mismatch between receiver and controller Bluetooth stacks

How to Fix Leica ERR-004 — Step by Step

1. Bring the field controller within 10 meters of the GNSS receiver. Bluetooth range in field conditions is often 15-20 meters — staying close prevents dropouts.
2. Check the field controller screen for a Bluetooth connection status indicator. If it shows disconnected, attempt to reconnect from Leica Captivate's connection manager.
3. On the CS35, navigate to Settings > Connections and reconnect to the GNSS receiver by selecting it from the paired devices list.
4. Verify the field controller Bluetooth is enabled and not in airplane mode. A battery-saving mode may have disabled Bluetooth.
5. Power cycle the field controller Bluetooth: turn it off, wait 5 seconds, then turn it back on. The receiver and controller should auto-reconnect.
6. If reconnection fails, un-pair and re-pair the devices. On the CS35: Settings > Connections > Bluetooth > unpair the receiver, then pair again.
7. Restart both the GNSS receiver and the field controller if re-pairing does not resolve ERR-004.

When to Send It In for Service

If Bluetooth consistently drops within a short range despite re-pairing, the receiver or controller Bluetooth hardware may be faulty. Contact an authorized Leica dealer.

Frequently Asked Questions

What is the Bluetooth range of Leica GNSS receivers?

Leica GNSS receivers use Bluetooth Class 1 with a rated range of up to 100 meters in open air. In practical field conditions with the operator's body between devices and potential RF interference, reliable range is typically 15-30 meters.

Can I use a cable instead of Bluetooth?

Yes — Leica GNSS receivers support RS-232 and USB cable connections as an alternative to Bluetooth. A cable is more reliable for stationary setup work where cable length is not a limitation.

Does Bluetooth Lost affect RTK corrections?

No — RTK corrections are received by the rover via UHF radio or cellular modem, independent of Bluetooth. Bluetooth Lost only affects data transfer between the receiver and the field controller. The receiver continues to maintain its RTK fixed solution during a Bluetooth outage.

Related Leica Error Codes

Leica GNSS ERR-003 Age of Corrections | Leica GNSS ERR-001 No Satellites