How to Diagnose No Signal and Baseband Issues on Android

Common Symptoms

• No Signal — Signal bars show empty, cannot make calls or use data
• Baseband Unknown — Settings > About Phone shows “Unknown” for baseband
• Emergency Calls Only — Device can only dial emergency numbers
• Invalid IMEI — *#06# shows null, 0, or incorrect IMEI

Step 1: Check IMEI

Dial *#06#. If IMEI is null or 0, the EFS/NVRAM partition is corrupted. This requires IMEI repair using Tfast Unlocker.

Step 2: Check Baseband

Settings > About Phone > Baseband version. If “Unknown”, the modem firmware is corrupted or missing. Flash the modem partition.

Step 3: Check SIM

Try a known-good SIM card. Check for SIM tray damage or debris. Try the SIM in another phone to rule out SIM issues.

Step 4: Network Settings

Reset network settings: Settings > System > Reset > Reset network settings. This clears saved Wi-Fi, Bluetooth, and cellular configurations.

Step 5: Firmware Solution

If software steps fail, the modem partition likely needs reflashing. Use Tfast Unlocker to flash just the modem/NON-HLOS partition, then perform IMEI repair if needed.

Hardware Causes

If all software solutions fail, the issue may be hardware: damaged RF chip, broken antenna connector, or water damage to the baseband IC.