Dexcom G7 stopped communicating with my t:slim X2 — what finally worked
I’m sharing this because it took me quite a while to figure out, and it may help someone else who runs into the same problem.
My daughter uses a Tandem t:slim X2 insulin pump with a Dexcom G7 sensor.
The G7 sensor itself was working normally — I could see glucose readings in the Dexcom app on the phone. The problem was specifically the connection between the G7 sensor and the t:slim X2 pump.
The sensor had been inserted about two days earlier.
What happened
The pump stopped receiving CGM readings. On the pump, I initially saw the red crossed-out antenna icon, indicating that the pump was not communicating with the sensor.
I contacted Dexcom Technical Support, and they referred me to Tandem. Tandem Support recommended restarting/resetting the pump.
What I did
I disconnected the infusion set from the body and put the pump into Storage Mode:
- Connected the Tandem USB cable to the pump and a power source.
- Held the Screen On/Quick Bolus button for approximately 30–40 seconds.
- Released it after the pump beeped/vibrated three times.
- Disconnected the pump from power and confirmed that the screen would not turn on.
- Reconnected it to power, and the pump turned back on after about 30 seconds.
This is consistent with Tandem's official Storage Mode procedure.
Important: the pump needed the cartridge to be loaded again
After restarting, the pump went through the initial screens and then reported that it did not detect the insulin cartridge.
I went through:
Options → Load
and followed the pump's instructions:
- confirmed that the infusion set was disconnected from the body;
- removed and reinstalled the filled cartridge;
- connected the tubing to the cartridge;
- performed Fill Tubing;
- confirmed that insulin had reached the end of the tubing;
- resumed insulin delivery.
Tandem states that after Storage Mode the pump's IOB is not retained and a cartridge must be loaded again before insulin delivery can resume.
Then came the G7 problem
After the pump returned to the Home screen, there were still no CGM readings.
Interestingly, the CGM menu did not simply show "Start G7 Sensor" in the way I expected. The pump appeared to consider the G7 session active, but it still wasn't receiving glucose data.
I did NOT press:
Stop G7 Sensor
This is important because Tandem states that once an active G7 session is manually stopped, the same sensor cannot be restarted and a new sensor is required.
What finally fixed it
I went back into the CGM section and found the option to enter the G7 pairing code.
I entered the same pairing code that had been used when the sensor was originally connected.
The pump connected to the existing G7 sensor.
The CGM readings came back and everything started working normally again.
So in my case, the sensor itself was fine. The Dexcom app was receiving data the whole time. The problem was that the t:slim X2 had lost/rejected its connection to the active G7 session after the pump had been restarted.
Tandem's documentation confirms that an active CGM session is stored on the sensor and can be rejoined after the pump has been shut down. Their current G7 instructions also describe entering the pairing code when reconnecting the pump to an active session.
My takeaway
If your Dexcom G7 is working on the phone but the t:slim X2 is not receiving readings, and Tandem has advised you to restart the pump, the sequence that worked for me was:
Storage Mode → restart pump → reload cartridge → resume insulin delivery → go to CGM settings → enter the existing G7 pairing code → reconnect to the active sensor.
And most importantly:
DO NOT press "Stop G7 Sensor" just because the pump isn't receiving readings. If the existing sensor session is still active, stopping it manually can mean losing that sensor and having to insert a new one.
This is my personal experience, not medical advice or a replacement for Tandem/Dexcom technical support. Always follow the instructions for your specific pump/software version and make sure you have an alternative way of monitoring glucose while the pump/CGM connection is unavailable.