Ender 3 (Pro & V2 & Neo & S1) Freezing During Print – Causes & Fixes

Noticing that your Ender 3 has randomly frozen during a print is definitely one of the most frustrating things you can come across on your 3D printing journey, whether it’s due to the amount of time, plastic, and electricity that has already gone to waste or the ambiguity of the problem’s source preventing you from starting another print.

In this guide, we will take you through all the potential factors that can cause your Ender 3 to freeze during the 3D printing process, help you isolate the one that’s creating the issue in your case, and discuss how you can resolve the problem you’re facing as swiftly as possible.

Ender 3 (Pro & V2 & Neo & S1) Freezing During Print – Causes & Fixes

With a few different problem candidates to put into consideration, finding out why the problem is happening in your case and fixing it all comes down to a trial-and-error process where you will need to observe how your Ender 3 behaves in each scenario and apply the correct solution based on your findings.

ender 3 freezing example

Using an Invalid or Corrupted G-Code File

An invalid or corrupted G-code file is one of the first factors that come to mind regarding the freezing problem you’re experiencing with your Ender 3, as the firmware won’t be able to interpret and run the commands contained within the G-code file in such a case, which can end up with the printing process getting stuck.

Invalid G-code file, in this case, refers to a file that doesn’t follow the format that Marlin firmware can read and interpret due to syntax errors, with examples such as not adding line breaks between each G-code command being one of the most common examples coming to mind.

While coming across an invalid G-code file should practically be impossible when you use reputable slicer software, such as Cura, to create G-code files, G-code files you have obtained directly from the Internet or performed manual modifications to can have this problem.

invalid gcode file example

In the above image, you can see an example of an invalid G-code file, where the comments that should be separated from the G-code commands with a semicolon (;) are appended next to the commands.

Additionally, in some cases, a G-code file name that’s too long; or one which contains special characters can also cause the file to become invalid, making it a good idea to keep the G-code filenames as simple as possible.

On the other hand, a corrupted G-code file refers to a file that has been damaged and doesn’t contain the original G-code data anymore, whether due to problems occurring during file transfer or issues regarding the disk it’s stored in.

Similar to an invalid G-code file, coming across a corrupted G-code file is practically impossible under normal circumstances where you create the file by slicing a model file on your own computer, but the likelihood of coming across a corrupted G-code file will naturally be higher if you received the file from an untrusted third-party source.

corrupted gcode file example

Regardless of how the G-code file is affected, the end result is that it won’t be structured in a way the firmware can read correctly, leading to issues such as your Ender 3 skipping the parts it can’t interpret and only running the commands that are still readable or freezing completely.

So, unless you have confirmed that your G-code file is invalid or corrupted and taken the necessary steps to remedy the problem already, our primary recommendation for ruling this problem out would be to exclusively use G-code files you have sliced on your own computer while ensuring that your slicer is always up-to-date.

Additionally, as G-code files are in human-readable format, you can always quickly check the contents of the file your slicer has produced before printing with it, where you can easily see if any glaring issues are present.

cura gcode file example

In the above image, you can see a snippet from a G-code file produced by Cura without any syntax errors or corruption that would cause issues.

Finally, it can be worth a try to use a different slicer than you usually do (we recommend Cura or PrusaSlicer) to be completely safe, as it’s practically impossible for two separate slicers to create the same exact problem, even if we assume that the problem was slicer-related, which is pretty low, to begin with.

Unreliable USB Connection (USB Printing Only)

If you’re printing over a USB connection, whether it’s utilizing Cura’s USB printing functionality or a 3D printing interface such as OctoPrint or Pronterface, an unreliable USB connection is another possible culprit that can cause the freezing issue you’re experiencing.

octoprint usb printing example

As there are many probable points of failure when printing over USB, whether it’s the USB cable you’re using or the USB port that the cable is connected to on your computer, it’s not exactly easy to identify the source of the problem in this case either.

So, our primary recommendation to quickly rule out USB connection-related problems would be to try printing with an SD card instead and see if the freezing issue reoccurs, as this is the most straightforward way to find out whether the USB connection is the culprit.

If the freezing problem does not occur when you print with an SD card, it’s practically a confirmation of the issue stemming from the USB connection.

In such a case, you can focus on the USB-related factors alone to solve the problem and will have an alternate way to use your Ender 3 without issues in the worst-case scenario.

When it comes to solving the USB connection problem, our first recommendation is to make sure that your computer doesn’t go into sleep or hibernation mode while the printing process is taking place, as this will stop the data transfer between your computer and your Ender 3, and effectively halt the print.

Next, we recommend changing the software you’re using for USB printing (especially if you’re using Cura’s USB printing feature, as it’s reported to cause issues), such as switching to Pronterface if you’ve been using OctoPrint, and vice versa.

pronterface example

Following that, another thing that can help you resolve the problem you’re facing is to connect the USB cable to a different port on your computer, which can, in some cases, be helpful in resolving problems regarding USB-connected devices.

If that doesn’t fix things either, our following recommendation would be to replace the USB cable, as the cable you’re using may be damaged in some way that causes the data transfer to become unreliable, even if there’s no visible damage when you inspect the cable from the outside.

Finally, our last recommendation if things still aren’t solved is to try connecting to start the printing process from a different computer, preferably one that you don’t need to actively use as printing is taking place, which will ensure that computer-related issues, such as a high CPU or memory load don’t create problems in data transfer.

In the scenario where the issue persists, a problem regarding the USB port on your Ender 3 becomes a considerable possibility, as you will have practically changed every other component involved in the USB printing process.

SD Card Corruption (SD Card Printing Only)

Provided that you’re using the standard method of copying a G-code file to a microSD card and inserting the microSD card into your Ender 3 to start a print, the corruption of the SD card you’re using is one of the common culprits that can cause the freezing problem you’re experiencing.

Additionally, it’s also worth mentioning that SD card corruption is even more likely to occur if you use a low-quality microSD card or microSD card reader, such as the ones that come together with the Ender 3, which are widely reported to be prone to eventually getting corrupted.

ender 3 sd card and reader

In an SD card corruption scenario, we have noticed that an identifiable case is the G-code file you’re transferring from your computer getting corrupted once it reaches the card, rendering the file unusable by your Ender 3.

To see whether your G-code files are getting corrupted during transfer, you can perform a checksum comparison between the G-code file you have on your local disk and the G-code file on the microSD card.

gcode file checksum test

If the MD5 hash of the G-code file on your local disk is not equal to the MD5 hash of the G-code file on the microSD card, this confirms that you’re experiencing a file corruption issue.

On the flip side, having the hashes match doesn’t necessarily mean that we can completely rule out the possibility of a bad SD card, as this problem can present itself in different ways, such as the entire filesystem getting randomly corrupted while your Ender 3 is reading it, which would be a strong indication of the card failing.

In fact, in some cases, even something as simple as taking the SD card out of your computer without correctly ejecting it can be the thing that creates the problem, as this can lead to data sectors actively being written on getting corrupted.

Finally, it’s worth mentioning that such cases will usually result in your computer not being able to read the SD card as well, with the filesystem showing RAW and requiring a format before you can read from (or write to) it again, which is another sign that would tell us something is wrong with the card.

sd card showing raw partition

Regardless of the cause, our first recommendation to rule SD card corruption out would be to print over USB, as this will allow you to see whether the issue you’re experiencing is SD card-related.

In the scenario where you don’t experience any issues when printing over USB, you will have confirmed that the source of the freezing problem you’re experiencing is SD card-related and have an alternative way to print without the freezing.

With this in mind, the next step to gather more information about the SD card problem would be to format the card (it wouldn’t be a bad idea to use a different USB port if possible), copy the G-code file once more, and try printing again, and see whether the freezing problem occurs in this case.

If the problem still exists, the natural next step would be to try again with a different SD card (preferably brand new) to find out whether the problem is related to that particular SD card you’ve been using, which usually is the case (especially with the stock Ender 3 SD card).

On the flip side, in the scenario where the problem still occurs, even with a brand new SD card, one last thing we recommend doing before considering the Ender 3’s SD card slot itself to be the problem would be to prepare (reformat & copy the G-code file) the SD card on a different computer to make sure that the issue isn’t stemming from the computer you’re using, as this is also a possibility that we have to consider.

Corrupted or Incompatible Firmware

Another factor that can lead to the freezing problem you’re experiencing on your Ender 3 is the usage of corrupted or incompatible firmware, as the firmware is responsible for practically any command that your printer runs.

If the freezing problem started occurring right after you have flashed new firmware to your Ender 3, especially from an untrusted third-party source where you can’t exactly be sure that the firmware file you obtained works as intended or whether it’s compatible with the particular Ender 3 model you have, it’s highly likely for the problem you’re experiencing to be firmware-related.

To quickly rule this possibility out, our first recommendation would be to flash the original firmware file that your Ender 3 came with, which, if you haven’t formatted or cleaned it, should be stored in the microSD card that shipped with your 3D printer.

ender 3 pro firmware file example

On the other hand, if you removed this file from the microSD card and can’t access it anymore, you can also easily retrieve it from the official Creality website, as the Downloads section has all the necessary firmware files for different models and mainboard versions of the Ender 3.

Since it’s entirely possible to end up with the wrong firmware file if you aren’t careful, as there are so many options available for various hardware, whether it’s a BLTouch-enabled version of the firmware or one that’s made specifically for an Ender 3 that has been upgraded with the high-temperature hotend kit, taking your time and ensuring that you have the correct firmware file is essential to avoid complicating things further.

As an example, if you’re the owner of a stock Ender 3 Pro with the v4.2.2 Creality mainboard, you can find the correct list of firmware files by navigating to the Ender 3 Pro section on the Creality website first and then grab the one that’ll work for your mainboard by locating the one labeled v4.2.2 from the list, while also ensuring that it’s not one for the Sprite extruder or the high-temperature hotend kit.

ender 3 pro firmware for v4.2.2 mainboard example

You can find your Ender 3’s mainboard version below (or next to) the Creality logo (or Creality3D text) on the mainboard itself, which you can access by removing the cover underneath the printer.

creality v4.2.2 mainboard identifying

Additionally, it’s also worth trying to flash another firmware from a reputable source if you’re running out of options and still haven’t found a fix, such as the TH3D Unified 2 Firmware, as this will allow you to completely rule out the possibility of firmware issues before taking more drastic steps, such as replacing the mainboard, considering that it’s practically impossible for two entirely different firmware to create the same exact problem.

th3d unified 2 firmware list

Finally, while it’s pretty unlikely for the firmware to be the source of the issue you’re facing if you’ve been using the same firmware successfully for some time now and haven’t made any changes to it, changing the firmware, considering that it barely takes any time, is still something to try as a last resort before moving forward with changes to the hardware side of things.

Damaged Wiring & Loose Connectors

Similar to any other issue you can experience on your Ender 3, problems regarding the wiring, whether it’s damage to the wires and the connectors or some of the connections being loose, can lead to the occurrence of the freezing problem you’re facing.

Problems related to the wiring are especially likely to be causing the problem in your case if you have recently opened up the mainboard cover and made modifications, whether it’s assembling your Ender 3 for the first time or installing new hardware, with the most common example being the installation of an automatic bed leveling sensor, such as the BLTouch.

In this case, our first recommendation would be to disconnect all the wires (including the power connector), examine both the wires themselves and the connectors on either side carefully for signs of damage, such as exposed or bent wires, loose connectors, burns, and practically anything else that comes to mind, and replace any damaged wires.

Once you confirm that all the wires are in good condition, the next step and final is to carefully connect each wire to its correct place, while ensuring that the connectors sit tightly in their places without any wobble, as the connection between a wire and the mainboard being loose will definitely create issues.

Since the wiring process can be tricky, we highly recommend having the wiring diagram for the mainboard your Ender 3 has open next to you while doing the wiring, as this will help you not to make any mistakes that can complicate things further.

Malfunctioning Mainboard

Finally, if none of the solutions so far has helped you fix the freezing issue you’re experiencing, it’s time to consider the mainboard itself as the source of the problem.

Similar to issues with wiring, a mainboard malfunction also is more likely if you have been making hardware modifications to your Ender 3, as it’s entirely possible to damage the mainboard in some way, whether it’s causing a short circuit or damaging one of the pins while you’re actively working on it.

That being said, it’s not unheard of for a mainboard to suddenly start having issues for no apparent reason, so we can’t really rule out the possibility of a mainboard malfunction if you haven’t opened up the mainboard cover recently either.

Regardless, if you have gone through all the solutions in our list so far and haven’t been able to fix the freezing problem you’re experiencing, a mainboard-related issue is the only culprit left.

Unfortunately, in the case of mainboard failure, the only viable solution is to replace the problematic mainboard with a new one, as there’s practically no way to find out which component of the mainboard creates the issue and fix it.

On the positive side of things, if your Ender 3 has an older 8-bit board, this can be an opportunity to upgrade your printer with a better one, such as the v.4.2.7 mainboard from Creality or the SKR Mini E3 from BIGTREETECH, which is something to consider when going down this road.


As bothersome as the freezing problem can be to solve, it’s definitely not one that will require you to replace your Ender 3 with a new one by any means, as it’s possible to swap any of the faulty components with a new one, even in the worst case scenario, and bring your Ender 3 back to working condition.

That being said, since it’s a whole lot more likely for something simple, such as the SD card causing your G-code files to be corrupted, to be the problem, as opposed to something a whole lot more complex to solve, such as mainboard failure, you should hopefully be able to get back to enjoying your Ender 3 without too much trouble.