EC200U-CN lost RF signal (CSQ 99,99) after upgrading to EC200UCNAAR03A14M08 firmware

Technical Subjects
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1

Hi Quectel Support,

I need help with my EC200U-CN module.

Module info:
Quectel EC200U
Revision: EC200UCNAAR03A14M08

Problem:
After upgrading firmware, the module lost network signal completely.

AT command results:
AT+CSQ → 99,99
AT+CEREG? → 0,0
AT+QCFG=“band” shows normal values.

SIM is detected and module works normally, but RF seems disabled and cannot find any LTE cell.

I suspect RF calibration or NV mismatch after upgrading to R03A14 baseline.

Could you please provide a stable firmware package such as:
EC200UCNAAR03A04M08 or EC200UCNAAR03A07M08 (.pac full package)

Module label:
EC200U-CN

Upgrade tool used:
UpgradeDownload

Thank you.

2

Dear @Ph_m_Cong_Th_c_B20DC ,

Thank you for reaching out and providing the details.

AT+CSQ = 99,99 together with AT+CEREG? = 0,0 means the module is not registered and is not currently camping on any LTE cell. After a firmware upgrade, this is most commonly caused by one of these conditions:

  • RF is forced into a non-normal mode (test mode or disabled RF state)
  • band/scan mode configuration is not suitable for the local network
  • antenna or RF path issue (antenna not connected, wrong connector/path, poor power supply during RF activity)
  • a wrong firmware package was used for the module variant, or NV/calibration was affected by the upgrade procedure

Before we consider flashing other firmware versions, please run the checks below and share the full outputs:

  1. Confirm firmware and basic radio state
  • ATI
  • AT+QGMR
  • AT+CFUN?
    Then do:
  • AT+CFUN=0
  • AT+CFUN=1
  • AT+CEREG?
  • AT+CSQ
  1. Ensure RF is not left in test mode
  • AT+QRFTESTMODE?
    If it is not 0, set it back:
  • AT+QRFTESTMODE=0
    Then reboot and re-check CSQ and CEREG.
  1. Confirm scan and RAT settings are correct for LTE
  • AT+QCFG=“nwscanmode”
  • AT+QCFG=“nwscanseq”
  • AT+QCFG=“iotopmode”
    If you are in an LTE-only deployment, nwscanmode should not be locked to an unsupported RAT.
  1. Try a controlled network selection test
  • AT+COPS?
  • AT+COPS=0
    Wait 1–2 minutes, then:
  • AT+CEREG?
  • AT+QNWINFO
    If still 0,0, run:
  • AT+COPS=?
    and share the result (this confirms whether any LTE cells are detected at all).
  1. Hardware confirmation
    Please confirm:
  • the LTE main antenna is connected to the correct MAIN port
  • the module supply is stable during attach (adequate peak current capability)
  • you can reproduce the same issue with another known-good SIM/operator in the same location

Kindly perform the above tests and share the full outputs. If the issue still persists after we confirm the RF state and network configuration, we will arrange the appropriate firmware package through mail.

Best regards,
Aghelan

3

Dear Aghelan,

Hello,

Thank you for your detailed guidance.

I would like to provide more background information on this issue.

Previously, I purchased around 500 EC200U modules from a Chinese reseller.
All modules were originally running OpenCPU firmware EC200UCNAAR02A06M08_OCPU.

Before upgrading, I verified the modules using some basic AT commands:

  • The SIM card was detected correctly
  • The modules were able to register to the network and had normal signal

However, after upgrading the firmware from EC200UCNAAR02A06M08_OCPU to EC200UCNAAR03A14M08, the LTE signal was completely lost:

  • AT+CSQ returns 99,99
  • AT+CEREG? returns 0,0

This issue is reproducible across multiple modules.

I am currently performing the checks you suggested (RF test mode, scan mode, RAT configuration, network selection, etc.) and will share the full AT command outputs once completed.

Based on the behavior, I am concerned that:

  • the firmware package may not be fully compatible with the original OpenCPU variant, or
  • NV / RF calibration data might have been affected during the upgrade process

Please advise if there is a recommended firmware package or recovery procedure specifically for upgrading from this OpenCPU version.

Thank you for your support.

Best regards,
Pham Cong Thuoc

4

Dear @Ph_m_Cong_Th_c_B20DC ,

Thank you for the clarification.

Based on your description, the root cause is the firmware package mismatch. Your modules were running an OpenCPU firmware (R02A06 OpenCPU), but they were upgraded using an R03A14 standard firmware package. Standard and OpenCPU packages are not interchangeable. If a standard package is flashed onto an OpenCPU variant (or vice versa), the module can enter an abnormal state where it cannot camp on LTE cells, which matches the behavior you see (CSQ 99,99 and CEREG 0,0 across multiple units).

In this situation, AT command configuration checks will not recover RF. The correct resolution is to re-flash the modules using the correct full firmware package that matches the module variant and the intended firmware type (OpenCPU or standard), using the recommended download method.

To proceed, please provide:

  1. the exact label on the module (full PN string from the module can)
  2. the exact firmware version that you flashed. (AT+QGMR)
  3. confirm whether you want the modules to remain OpenCPU or move to standard firmware

After that, we will arrange the correct recovery package through mail and share the correct flashing procedure for your case.

Best Regards,
Aghelan

5

Dear Aghelan,
Please find the requested information below:

Module label (full PN on module can):
EC200UCNAA-N05-SGNSA

Previous firmware running on the modules (before issue):
EC200UCNAAR02A06M08_OCPU

Firmware that was mistakenly flashed and caused RF abnormal state:
EC200UCNAAR03A14M08

Current status:
Some units have been temporarily recovered back to EC200UCNAAR02A06M08_OCPU and RF is working again.

Our request and final target:
We would like to move to Standard AT firmware only.
We no longer plan to use OpenCPU firmware.
Our application will be developed using AT commands (LTE + GNSS), so a stable Standard AT package for EC200UCNAA-N05-SGNSA would be ideal.

Could you please provide the correct full recovery package and flashing procedure to migrate safely from the current OpenCPU firmware to Standard AT firmware?

Thank you very much for your support.

6

Dear @Ph_m_Cong_Th_c_B20DC ,

Thank you for confirming the module PN EC200UCNAA-N05-SGNSA and the firmware history.

From your description, the root cause is that EC200UCNAAR03A14M08 standard AT firmware is not compatible with the OpenCPU variant baseline you were using, so the module cannot operate RF normally after that mismatch flash. The fact that RF recovers after restoring EC200UCNAAR02A06M08_OCPU further confirms this is a firmware package compatibility issue, not an antenna, SIM, or band setting issue.

Kindly check your mail inbox, for further procedure.

Best Regards,
Aghelan