Quectel EC25 Mini PCIe USIM detection problem (USIM_VDD=0V)

[Robin_Xiao]

@Kyson

Yes, that’s my plan ultimately, but just want to find some documentation to guide along troubleshoot rather than trial and error to reverse engineer.

Given that the 0V Vdd isuess does not happen consistantly, and currently unsure how to re-produce. Even if the resistor is working after soldered, I have no ways to know this is exactly the solution.

Also 2 reasons led me to ask for background logic:

1. Most of the terminal devices with EC25 works flawlessly and non of them has the pull up resistor
2. I do have another brand terminal that uses EC25, and its manufacture also decided to skip this pull up as well, it must be for a reason

[Kyson]

Dear Robin,
For such issue, there have no such document to guide you how to find the reason, just share some tips with you. Hopefully it is useful to you. Thanks!
1.The most important is to follow up the reference design to design your own circuit.
2. About the SIM card issue, it is better to check whether the SIM slot have any connect issue, and use AT+CPIN? to check whether the module have recongize the SIM card.
3.If not, it is better to check the voltage of SIM_VDD, we recommend you use oscilloscope to check it from power on the module.
4. You also can check the waveform of SIM_CLK, SIM_DATA to check whether there have any interference on it. Of course, you need to check the layout before do it. Thanks!

[Robin_Xiao]

I tried to add i nthe 15k pull up resistor and made no improvement, the sim circuitry is exactly same asm refernce. So still stuck…

I did manage to speak with one of you company rep who explained that on boot logic. It detect sim with both 3V and 1.8V, for 3 times, if all 3 times failed, then VDD is shut off.

Still doesn’t explain why the Sim cant be detected

Anyone got any further ideas? Or anyone got any luck with a scope? I don’t have one.

@Kyson

Here’s another user with same issue

Quectel ec25 mini pcie sim detection problem

Hello every one, We use Quectel EC25 Mini PCIE, there are many devices at field. Some devices internet connection is lost. Even if device turn off and turn on, GSM module does not recognize simd AT+CPIN gives error or gives out put sim not ready. On order to recognize sim again, we need to take sim off and push it in again. When we check logs, its connected to GSM module, 1 minute later, GSM Module is not able to recognize SIM. Thank you…

[SmartEq_Bilisim]

@Robin_Xiao

Anyone got any further ideas? Or anyone got any luck with a scope? I don’t have one.

Problem is, if voltage fluctuates than this problem happens.
First, Quectel must accept that problem and try to solve it.

In one thread @Kyson says send AT+CFUN = 0 than send AT+CFUN=1 but it does not work too.

This problem is not a problem that customer can solve. I do not know why Quectel side insist to deny this problem. It is not a problem that is little.

This is very important problem. Think it a little, I sell a device than it does not connect internet. Because it does not detect sim card.

You can also create that problem at office too. While device is working fluctuates voltage and than that happens.

So, guide to solve that problem by software.

[Kyson]

@Robin_Xiao

I did manage to speak with one of you company rep who explained that on boot logic. It detect sim with both 3V and 1.8V, for 3 times, if all 3 times failed, then VDD is shut off.

Dear Robin_Xiao,
The module’s behavior of SIM detect is the same as the above said, you can check the waveform of SIM_VDD start from power on module, and confirm whether it is the same as we said. If it is different, it may be related to module hardware or software, if it is the same, you may need to check the external SIM card circuit to confirm whether there have any abnormal, you can try to weld another SIM holder connect to module SIM pins to confirm it. Thanks!
@SmartEq_Bilisim In order to solve the issue, we need to confirm where is the issue firstly. Thanks! What we can confirm is that we have test the module hardware and software before you get it, and the module is normally. Now what we need to confirm your test method, your hardware design…Thanks!

[ginkiter]

Whe have the same problem too. EC25-E does not recognize SIM cards. We welded card holder to the board, but it does not work:
minicom *********
at+cfun=1
OK

+CPIN: NOT INSERTED

qmicli:*********
root@t1042d4rdb:~# qmicli --device=/dev/cdc-wdm0 --uim-get-card-status
[/dev/cdc-wdm0] Successfully got card status
Provisioning applications:
Primary GW: session doesn’t exist
Primary 1X: session doesn’t exist
Secondary GW: session doesn’t exist
Secondary 1X: session doesn’t exist
Slot [1]:
Card state: 'error: no-atr-received (3)
UPIN state: ‘not-initialized’
UPIN retries: ‘0’
UPUK retries: ‘0’
root@t1042d4rdb:~#

[Kyson]

If that, it is better to check the waveform of SIM_VDD, SIM_DATA,SIM_CLK of the module start from power on module.Thanks!

[Aamina_Hassan]

I am using EC20CEHCR06A03M1G on sixfab rasberry 3g/4g Hat, and I am unable to detect sim, even after trying several time. Please help me get the exact issue with the board. I have at+cfun=1, I tried at+qsimdet=1,0
OK
at+cops?
+COPS: 0

OK
at+cops=1
ERROR
at+cpin?
+CME ERROR: 10

and much more than that, but its failing badly. I have tried with two different sims, each working fine on the mobile.

[Kyson]

If that, please check the hard design circuit of SIM card in your board. Thanks!

[SmartEq_Bilisim]

Hi again,
After a long and tedious process, we realize that problem is about SIM card connector’s pin. Their contact are are not wide pins are thin.

Thank you.

[yonatanGriiip]

Thank you all, this thread was very helpful.
I Believe my system is suffering from the same issues.
Sim card sometimes not detected and it solved by rebooting the system (without touching it).

Can please provide More details/photos of good vs bad contacts?

[Micas]

Hi Sir,

Can you please clarify what are the dimension of a wide vs thin pins?
The contact should be wide, is what you sugest, right?
Thank you very much

[emone]

I encountered the same problem.

[emone]

I measure between SIM_VDD and SIM_DATA, the result is around 10K Ohm pull-up on Mini PCIe EVB Kit
It’s not 15K Ohm pull-up following datasheet.

[emone]

After reset modem via reset pin.

After AT+CFUN=1, It is still not finding sim card.

[Vincent1]

Hello,

I am experiencing an issue with several Quectel EG25-G modules. Out of a batch of 200 boards, 7 modules fail to start properly**, even though the hardware configuration is strictly identical across all of them.

VBAT_BB and VBAT_RF supply: Stable at 3.8 V

USB_BOOT: 0 V (pulled to GND via pull-down)

PWRKEY: Low pulse at 0.8 V for 500 ms, then returns to 1.38 V

RESET_N: 2.3 V (high level, left floating)

VDD_EXT: Measured at ~2 mV (instead of the expected 1.8 V)

Module current consumption: ~100 mA

Verified power-up sequence and PWRKEY timing/logic levels

USB_BOOT confirmed at 0 V → module is not in DLOAD mode

RESET_N left floating, measured at 2.3 V → no active reset

VDD_EXT remains at ~2 mV, whereas a running module typically outputs 1.8 V

All components connected to VDD_EXT (pull-ups, buffers, UART bridge, etc.) have been removed to rule out any external short or overload.

Additionally, the USIM is not detected — could this be a consequence of the module not powering up correctly?

Do you have any explanation for this abnormal behavior?

Is this a known issue affecting certain batches of EG25-G modules?

Is there any recommended test procedure to confirm whether the module is properly booted or a method to force its power-up?

Thank you in advance for your support.

Best regards,