# Sensor went offline, is it dead? **URL:** \ **Category:** Troubleshooting\ **Created:** [April 30, 2022, 1:23am UTC](https://community.purpleair.com/t/sensor-went-offline-is-it-dead/557 "2022-04-30T01:23:32Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Azer](https://sea2.discourse-cdn.com/flex020/user_avatar/community.purpleair.com/azer/32/418_2.png) [@Azer](https://community.purpleair.com/u/Azer)\ **Post date:** [April 30, 2022, 1:23am UTC](https://community.purpleair.com/t/sensor-went-offline-is-it-dead/557/1 "2022-04-30T01:23:33Z")
Hi, I’ve run the ‘Carrum’ sensor for a couple of years now. I have a ping alert on the sensor, so I know that at about 5pm yesterday afternoon it dropped off my network, which very rarely happens. I have power cycled it a number of time, even giving it 5 minutes before turning it back on. I can see the red light inside, but it never reconnects and doesn’t broadcast the wifi network. I have rebooted my APs (UniFi) as a precaution. Is it dead? I know these do over the air updates, is there a chance one of these has bricked it? ---
**Author:** ![Ethan](https://sea2.discourse-cdn.com/flex020/user_avatar/community.purpleair.com/ethan/32/177_2.png) [@Ethan](https://community.purpleair.com/u/Ethan)\ **Post date:** [May 2, 2022, 3:43pm UTC](https://community.purpleair.com/t/sensor-went-offline-is-it-dead/557/2 "2022-05-02T15:43:34Z")
Hi @Azer, in this case, let’s try using the PurpleAir utility to see if we can get your sensor’s WiFi network to appear again. With this utility, you can reflash the firmware on your device. You will need a micro-USB cable to complete this task, and the cable has to be a data transfer cable. You can download and install the PurpleAir utility here: macOS: [https://static.purpleair.com/desktop-utility/PurpleAir-1.0.6.pkg](https://static.purpleair.com/desktop-utility/PurpleAir-1.0.6.pkg) (You may need to right-click on the file and choose Open for it to run) Windows: [https://static.purpleair.com/desktop-utility/PurpleAir-1.0.6.exe](https://static.purpleair.com/desktop-utility/PurpleAir-1.0.6.exe) Once the utility is installed, connect your sensor to your computer using your micro-USB cable. Select the appropriate com port in the utility under "Select a Serial Port” and press "Connect” to see the sensor output. Under "Select a Flash Action,” select the firmware .bin file and click "Flash” to update the firmware on the sensor (The current firmware version is 6.01). Once the firmware is downloaded, check the list of available WiFi networks for a network called PurpleAir-\*\*\*\* (The \*’s will be the last two to four characters of your sensor’s device ID). Connect to it and follow the WiFi configuration instructions on the pop-up window if you see this network. If you do not see this network, take a screenshot of what you are seeing so we can continue to troubleshoot. ---
**Author:** ![bexcran](https://sea2.discourse-cdn.com/flex020/user_avatar/community.purpleair.com/bexcran/32/1898_2.png) [@bexcran](https://community.purpleair.com/u/bexcran)\ **Post date:** [January 17, 2023, 2:05am UTC](https://community.purpleair.com/t/sensor-went-offline-is-it-dead/557/3 "2023-01-17T02:05:06Z")
I know this is an old topic, but since I’ve just had the same issue with my PA-II sensor I thought I’d reply. I ended up having to do a factory reset by choosing “Erase ALL memory” then flashing the SensorFirmware6.02f.bin file. In my case, the PA-II wasn’t connecting to my WiFi because it was stuck in an infinite reboot loop. The serial output showed: ```auto ets Jan 7 2023,rst cause:2, boot mode:(3,6) load 0x4010f000, len 1384, room 16 tail 8 chksum 0x2d csum 0x2d v8b899c12 ~ld ets Jan 7 2023,rst cause:2, boot mode:(3,6) ... ``` I wish the existence of the PurpleAir Utility was more obvious, because in the past I’ve thrown away a PA-II sensor that stopped working, since there’s no obvious way to do a factory reset to get it working again! ---
**Author:** ![bexcran](https://sea2.discourse-cdn.com/flex020/user_avatar/community.purpleair.com/bexcran/32/1898_2.png) [@bexcran](https://community.purpleair.com/u/bexcran)\ **Post date:** [January 17, 2023, 2:21am UTC](https://community.purpleair.com/t/sensor-went-offline-is-it-dead/557/4 "2023-01-17T02:21:30Z")
I meant to also say: since it appears the PurpleAir Utility is a UI for ESP tools it might be useful if that was documented (if it’s not already!) so that people running other OSes like Linux can also recover their device. ---
**Author:** ![Ethan](https://sea2.discourse-cdn.com/flex020/user_avatar/community.purpleair.com/ethan/32/177_2.png) [@Ethan](https://community.purpleair.com/u/Ethan)\ **Post date:** [January 17, 2023, 4:54pm UTC](https://community.purpleair.com/t/sensor-went-offline-is-it-dead/557/5 "2023-01-17T16:54:59Z")
We have an article on the PurpleAir Utility here: [The PurpleAir Utility](https://community.purpleair.com/t/the-purpleair-utility/673). We hope this proves helpful. However, if there are updates that should be made, please let us know.