Emergency Question - Sensor related

We just changed out the transmitter/sensor and we got a “Sensor Failed, Replace Sensor”. It’s a brand new sensor, and transmitter.

It was 1/2 way through calibrating when it got an hour glass, then question marks, then vibrated with that message.

One mistake we did make is that we REMOVED the sensor/transmitter before stopping the session (slipped our minds). I stopped both sensors nearly immediately after they were removed, though.

Anyone have any idea what’s going on and what we should do in this situation?

I have often noticed failed sensors during times when my transmitter is about to die. The receiver doesn’t say it is a transmitter problem, it always says “sensor”, but it always ends up to be caused by the battery being about to die.

I recently had the same situation, and my transmitter was only 1 1/2 months old, so it was not due for replacement. I did several restarts, and it kept giving me the ??? or hourglass symbol. I restarted it 3 times!

I called Dex and they said they would replace the transmitter for me. I swapped out the transmitter with the other (new) one I had, and it resolved the problem.

The key for me to see it was the transmitter - I tried several restarts, and also tried a new sensor, same problem. But once I put in a new transmitter (but used a sensor that had just failed twice a few minutes previously), it worked.

So bottom line, even though it is a brand new transmitter for you, it is possible it is bad. I found that out after many retries.

Call Dex, and explain it to them. They should swap it for you.

Also, look on your receiver and look at transmitter status and see if it says low battery.


No battery message. It’s reading the new transmitter information.

On the receiver (not sure if they have the same setup on the phone):
Settings ==> Transmitter ==> Transmitter Info ==> Transmitter Battery

What does it say there? Does it say “OK”?


We called Dexcom and they want us to install a new sensor and they’ll be sending is a replacement. We’ll see if this fixes the problem.

New sensor installed…we’ll see if it was just a sensor problem. The representative we spoke with freaked out when I suggested that perhaps we should try “re-seating” the transmitter. He said NEVER EVER do that…something about the wire breaking off inside his skin and requiring surgery. Uhhhh…okay? We’ve re-seated the transmitter multiple times w/o any of this happening.

Hopefully the sensor will fix it. The reason I mentioned the transmitter is because I just went through that whole thing a few days ago! And same message - “Sensor Failed, Replace Sensor”.

And after first restarting, and then swapping the sensor and still seeing the same problem, once I swapped the transmitter it worked perfectly.

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I told him that too. He said if this sensor causes an issue that we can consider the transmitter but at this point, from all indications he has from our description of the problem, he thinks it’s sensor…time will tell. It’s in the warm-up phase currently, 1/8 complete…no problems so far. The last one didn’t crap out until about the 1/2 mark.

For what it’s worth, when I was having the transmitter problem it failed pretty early in the warm-up phase. So you might have gotten it fixed. :crossed_fingers:

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Update: The new sensor works now! w00t! Thanks @Eric


Great news!

Gotta add this to my list of strange crap to know in the future. :stuck_out_tongue:

2 years of using the CGM and I’ve never had a “Sensor” failure.

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Did you try a 2nd restart before you swapped the sensor?

In the future that could just be a time waster, may not help, but it might save a poke.

I usually try another restart first, just because it is easy. After that, I do a sensor swap.

The only downside to trying a restart first is the time it might waste. :face_with_raised_eyebrow:

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Yeah, 3 attempts.

The strange part is that the old transmitter was NOT dead yet either. We received the message two days ago that the transmitter had 2 weeks remaining. So, we had hoped we could use the old transmitter. But when we stopped sensor, it gave us the message that we need to use a new transmitter…so we effectively lost about 12 days on the transmitter. That’s why we were even going with the new transmitter. We had hoped we could just stop session, change sensor, restart session on old transmitter.

That’s what puzzled me too, my transmitter died 1 1/2 months before it was due. But since Dex is replacing it, it’s no big deal.

Well, they’re not replacing any transmitter for us…only the sensor we lost. We’ve still lost those 12 days on the old transmitter.

Did you ask them about it? Seems like they should do something about it.

No, forgot to even mention it. According to Erin, though, when we get the low batter warning on the 2nd transmitter (the one we just started today), they’ll send us 2 more.