Notice on GPS Positioning Issues in Devices with MTK 2503D Chips

Date: August 18, 2025
Author: Shenzhen Jimi IoT Co., Ltd.

Introduction

Recently, we identified an abnormal issue affecting the GPS functionality of certain devices equipped with the MTK 2503D chip (with a built-in MT3333 positioning chip). After technical investigation, this problem has been confirmed to stem from the GPS week rollover.

As a result, some devices may reset their positioning time to January 1, 2006, and the GPS status may not remain stable.

Affected Devices

• Impacted: 2G locator products with MTK 2503D chips
• Not Impacted: 4G locator products

What’s Happening?

The GPS week rollover issue causes the system timestamp to reset, which affects time synchronization. While location accuracy (longitude, latitude, and speed) generally remains correct, the reported time becomes abnormal.

Immediate Solutions

1. Server-Side Correction

We recommend implementing a correction mechanism for GPS timestamps reported by affected devices:

• Trigger Condition:
  If the device-reported UNIX timestamp is less than 1451606400 (January 1, 2016 UTC), apply correction.
• Correction Formula:

• Corrected Timestamp = Device-reported Timestamp + 619315200
  
  

• Example:
  • Reported GPS timestamp: 1136105465 (2006/01/01 16:51:05)
  • Corrected GPS timestamp: 1755420665

2. Terminal-Side Adjustment

You may configure device positioning modes as follows:

• GPSMODE,0# (BeiDou-only mode):
  • Time is normal, but performance may degrade and positioning may fail often.
  • Recommended only when server correction is not possible.
• GPSMODE,1# (GPS-only mode):
  • Time is abnormal, but positioning performance is stable.
  • Latitude, longitude, and speed data remain accurate.
  • Recommended as the best temporary solution.

Our Commitment

Our R&D team is working closely with MTK’s original factory to develop a firmware patch. Once the OTA firmware update is available, we will immediately notify users and provide update services to fully resolve the issue.

We sincerely apologize for the inconvenience and thank you for your continued trust and support. As always, we remain committed to providing reliable and high-quality GPS products and services.