A PM01 modem that does not register on the GSM network requires a controlled comparison with a working unit. The available evidence identifies the registration response, signal-quality response, antenna, SIM card, documented factory reset, and warranty repair as the relevant decision points.
Confirm the Registration Failure
Query the modem with AT+CREG. The expected response in the available evidence is 0,1. If the modem returns another value, record the complete response rather than interpreting it without the PM01 documentation.
AT+CREG
AT+CSQ| Check | Evidence-based result | Decision |
|---|---|---|
| Network registration |
AT+CREG should return 0,1
|
A different response confirms that registration is not in the stated expected condition. |
| Signal quality | The reported AT+CSQ value is ambiguous: both 7,0 and 0,7 appear in the evidence. |
Repeat the command and preserve the exact order and punctuation. |
Repeat the Signal Test
Run AT+CSQ again. Do not diagnose from the recorded value because the evidence contains conflicting entries: +CSQ: 7,0 and +CSQ: 0,7. Capture the modem's exact response directly from the terminal, then evaluate it using the documentation for the installed PM01 modification.
Isolate the External Components
The antenna and SIM card were taken from a working unit, which reduces the likelihood that either external component caused this specific failure. For a repeatable test, install the known-working antenna and SIM in the affected modem, issue both commands, and compare the results with the working modem under the same conditions.
- Connect the known-working antenna and SIM card to the affected PM01.
- Record the complete
AT+CREGandAT+CSQresponses. - Repeat the same queries on the working modem and compare the raw responses.
Reset or Escalate the Modem
A documented factory-reset method involving shorted outputs was reported to restore one modem, but the evidence does not identify the output terminals or procedure. Use only the reset instructions for the exact PM01 modification; do not guess which terminals to bridge. If the reset does not restore a 0,1 registration response while the known-working antenna and SIM remain installed, send the modem for warranty repair with the fault description No registration in GSM network
. Include the full modification, manufacturing date, serial number, and captured command responses.
FAQ
What should AT+CREG return on the PM01?
The available evidence identifies 0,1 as the expected AT+CREG response. Record and report the complete response if the modem returns another value.
Is the PM01 signal reading 7,0 or 0,7?
The evidence contains both values, so the recorded result is ambiguous. Repeat AT+CSQ and copy the exact response directly from the terminal.
When should a PM01 with no GSM registration be repaired?
Escalate it for warranty repair if a documented reset fails and the modem still does not return 0,1 with a known-working antenna and SIM. State the fault as No registration in GSM network
and supply the modem identification details and command results.
