Q1. My phone often shows "No Service" or doesn't detect my SIM card until I restart it. What causes this?

This is a common software issue reported for the BQ-5519G. It is often caused by a bug in the modem firmware. Flashing the official stock ROM reinstalls the entire radio firmware and is the most reliable way to fix this network instability.

Q2. I constantly get the error "System UI has stopped" and the phone freezes. How do I fix this?

This error indicates a critical corruption of the Android user interface files. A factory reset may not be enough to fix it. A complete firmware flash, as described in this guide, will replace the damaged files and resolve the freezing and error messages.

Q3. Will flashing this firmware make my phone faster?

It will restore the phone to its original factory speed. Over time, accumulated junk files and apps slow the device down. A clean flash removes all of this, but please note that with 1GB of RAM, the phone is designed for basic tasks, and heavy multitasking will still be slow.

BQ Mobile BQ-5519G Jeans Firmware (Stock ROM)

The BQ Mobile BQ-5519G Jeans is a budget-friendly smartphone from 2019, distinguished by its unique denim-textured back cover. It runs on Android 9 Pie (Go Edition), a lightweight operating system designed for devices with 1GB of RAM. Over its lifespan, users have reported specific software issues, most notably unstable network connections where the SIM card is not detected, persistent “System UI has stopped” errors, and frequent system freezes. For users facing these problems, a full re-installation of the official stock firmware is the most effective way to restore the phone’s stability and core functionality.

ℹ️ Important Note:
This phone is powered by a UNISOC (Spreadtrum) chipset and requires the SPD Upgrade Tool for flashing. This procedure will completely erase all your personal data. Ensure you have backed up your important files before you begin.

⚠️ Prerequisites: Before You Begin

Click Here for the Essential Pre-Flashing Checklist

Backup Your Data: All your contacts, photos, and files on the phone’s internal storage will be permanently wiped.
Charge The Battery: To prevent the phone from shutting down during the update, ensure the battery is charged to at least 50%.
Windows PC & USB Cable: You will need a Windows computer and a standard micro USB cable to perform the flash.

📱 Quick Device Specifications

Device: BQ Mobile BQ-5519G Jeans
Chipset: UNISOC SC7731E
Display: 5.5″ IPS (960×480)
Operating System: Android 9 Pie (Go Edition)
RAM: 1GB
Storage: 16GB
Battery: 2500 mAh (Removable)

🛠 Required Tools & Downloads

File / Tool	Download Link
SPD Upgrade Tool	Download Tool
UNISOC/SPD SCI USB Drivers	Download Drivers

⬇️ BQ Mobile BQ-5519G Jeans Stock ROM / Firmware

Android Version	Build Number	Chipset	Download Link
9 Pie (Go Edition)	V01_191219	UNISOC SC7731E	Download (MediaFire)

Quick Steps to Flash BQ-5519G Jeans Firmware

Download and install the SPD SCI USB Drivers on your Windows PC.
Extract the firmware ZIP file (BQ_5519G_Jeans_..._9.0_SPD.zip) to get the .pac file inside.
Extract and run the SPD Upgrade Tool (UpgradeDownload.exe).
Click the single gear icon (“Load Packet”) and select the firmware .pac file.
Click the play icon (“Start Downloading”). Power off your phone completely.
Press and hold the Volume Down key, and while holding it, connect the phone to the PC. The tool will detect the phone and start flashing. You can release the key once the progress bar appears.
A green “Passed” message will appear upon completion. Disconnect your phone and power it on.

For a more detailed, step-by-step guide on this process, please refer to our main tutorial:
👉 Full Tutorial: How to Flash Firmware with the SPD Upgrade Tool

❓ Frequently Asked Questions (FAQs)

Q1. My phone often shows “No Service” or doesn’t detect my SIM card until I restart it. What causes this?: This is a common software issue reported for the BQ-5519G. It is often caused by a bug in the modem firmware. Flashing the official stock ROM reinstalls the entire radio firmware and is the most reliable way to fix this network instability.
Q2. I constantly get the error “System UI has stopped” and the phone freezes. How do I fix this?: This error indicates a critical corruption of the Android user interface files. A factory reset may not be enough to fix it. A complete firmware flash, as described in this guide, will replace the damaged files and resolve the freezing and error messages.
Q3. Will flashing this firmware make my phone faster?: It will restore the phone to its original factory speed. Over time, accumulated junk files and apps slow the device down. A clean flash removes all of this, but please note that with 1GB of RAM, the phone is designed for basic tasks, and heavy multitasking will still be slow.

🔧 Device Troubleshooting

The phone is stuck in a bootloop after a successful flash: This can happen if old data conflicts with the new system. Boot into recovery mode (usually Power + Volume Down), and perform a “Wipe data/factory reset.” This will allow the phone to boot correctly.
SPD Upgrade Tool gets stuck on “Checking BAUD”: This is the most common flashing error and points to a driver or connection problem. Ensure you have installed the correct SPD SCI drivers. Try a different USB port and a known-good USB cable. Critically, make sure the phone is fully powered off before you press and hold the Volume Down button and connect it to the PC.
I forgot my Google account and am stuck after a reset (FRP Lock): Flashing this firmware will completely wipe the phone, which includes removing the FRP lock. After the flash, you will be able to set up the device with a new Google account.