Can't pair pump

You opened the GlycemicGPT phone app, tapped Pair pump, and something went wrong -- the app didn't find the pump, the pairing code was rejected, or the connection drops immediately. Here's the path through the most common causes.

Check pairing prerequisites first

These are the boring causes. Walk through them before assuming anything's broken:

Bluetooth is on on your phone (Settings → Bluetooth)
Location is enabled for the GlycemicGPT app (Android requires Location permission for any Bluetooth scan; this is an OS-level requirement, the app does not track your location)
The pump is in pairing mode -- on Tandem t:slim X2, this is Options → Bluetooth Settings → Pair Device. The pump shows a 6-digit code while it's in pairing mode. The code times out after a couple of minutes -- if the app didn't connect by then, restart pairing on the pump.
The pump is within Bluetooth range -- a couple of meters, ideally on the same desk as your phone during pairing. Range can be much shorter through walls.
Battery on both devices -- a low-battery pump or phone can flake out during Bluetooth handshakes.

Symptom: the app doesn't find the pump at all

The app shows "Searching..." and never lists your pump.

Is the pump actually advertising?

Tandem pumps only advertise themselves over Bluetooth when in pairing mode. If you opened pairing on the pump but the app didn't see anything, try:

Cancel pairing on the pump (back out of the menu)
Force-stop the GlycemicGPT app on your phone
Open the app again, tap Pair pump
Then open pairing on the pump

Order matters here -- the app needs to be actively scanning when the pump starts advertising.

Is another app already connected to the pump?

Tandem pumps only allow one Bluetooth connection at a time. If your phone (or another phone) is already connected to the pump via the official t:connect app or any other Bluetooth app, GlycemicGPT can't connect.

Disconnect the other app first:

In the official t:connect app: Settings → Pump Settings → Forget pump (or similar -- consult t:connect documentation)
On the phone: Settings → Bluetooth → find your pump, tap settings/info, tap Forget

Then retry pairing in the GlycemicGPT app.

Is your phone too old?

The app requires Android 11 or newer (API 30+). On older phones, Bluetooth permissions and stack behavior differ enough that the app may scan but not see anything. Check your Android version: Settings → About phone → Android version.

Symptom: the pump shows up but the pairing code is rejected

The app discovers your pump, but when you enter the 6-digit code, it returns an error.

Re-enter the code carefully. It's easy to mis-read a 6 as an 8 on the pump's screen.
Don't let the code time out. The pump only accepts the code for a couple of minutes after pairing mode starts. If you took too long, restart pairing on the pump and try again.
Use the correct field. GlycemicGPT shows two fields during pairing -- one for the pump's code, one to confirm. Make sure you typed the code in the right one.

Symptom: pairing succeeds but the connection drops within seconds

The pairing handshake completes, the app shows "Connected" briefly, then drops back to "Disconnected" or "Searching."

Is your phone's battery optimization killing the app?

Android aggressively suspends apps in the background. For Bluetooth pump connections to stay live, the app needs to be exempted:

Settings → Battery → Battery optimization
Find GlycemicGPT in the list
Set to Don't optimize (or "Unrestricted" / "No restrictions" -- the wording varies by manufacturer)

Samsung phones additionally have a "Sleeping apps" list (Settings → Apps → GlycemicGPT → Battery). Make sure GlycemicGPT isn't on it.

Is the pump's Bluetooth flaky?

Tandem pumps occasionally have Bluetooth issues that resolve with a power cycle:

Power off the pump (consult your pump's manual; this is not "remove the battery" -- use the proper power-off sequence)
Wait 10 seconds
Power back on
Try pairing again

This is also a good thing to try after a pump firmware update.

Is your phone case interfering?

Some metal phone cases or cases with embedded magnets degrade Bluetooth signal. If you've got a heavy-duty case, try pairing without it once and see if that changes anything.

Symptom: "the pump is paired but data isn't flowing"

Pairing finished without errors, the app shows "Connected," but no glucose / insulin data shows up. That's a different problem -- see BG isn't updating.

Tandem Mobi specifically

The Tandem Mobi pump uses the same Bluetooth protocol as the t:slim X2, but the platform has not been verified against physical Mobi hardware (see README Mobi note for the disclaimer). Pairing with Mobi may work but is at your own risk. If you have a Mobi and successfully pair, please open an issue reporting your experience -- it helps the project understand whether Mobi support is solid in practice.

Still stuck?

Capture this and bring it to Discord.

Before posting logs publicly, redact sensitive values. Logs may contain emails, bearer / API tokens, auth headers, account IDs, pump serial numbers, and Bluetooth device identifiers. Replace anything you wouldn't want a stranger to have with [REDACTED], or send the unredacted version via Discord DM to a maintainer instead of posting in a public channel.

Your pump model (t:slim X2, Mobi)
Your phone model and Android version
What the app shows (Searching / Found / Connected / Error message)
Whether the pump is currently paired with anything else (t:connect, Sugarmate, etc.)

Can't pair pump

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