Cracking the Code: What Those MIDMARK M9/M11 Error Codes Really Mean (Part 1)

You’ve seen them pop up on the display of your MIDMARK Ultraclave.

Instead of the benevolent, serene communication of time, temperature and pressure that you’re used to seeing, now you’re getting this jarring, cryptic, malevolent message of DOOM. The hidden meaning of which you have no idea!


Uh, oh.

“What just happened?”, you ask.

“What meaneth this strange communication?”

And (you may be thinking), “Why did THIS have to happen on MY shift?!”

Sorry. We can’t help you with that last question.

But we can certainly help you with the first two!

De-Mystifying MIDMARK Error Codes: Old vs. New

The first thing you need to know in order to understand what those codes mean is this:

Which version of the Ultraclave do you have? The “old’ one, or the “new” one?

There is an easy way to tell the difference.

“The display gives it away!”

Without getting too technical, here is the visible difference:

  • Old Version => Red Digits in an LED Display (LED=light-emitting diode)
  • New Version => Green LCD (LCD=liquid crystal display)

Basically, if your M9 or M11 has red LED digits in the display, then it is without a doubt the “older” version.

If it has a green LCD display with darkish-green digits, then it is most certainly the “newer” version.

Guess which one this is…

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Mind this difference well, my friend. For, herein lies the “fool-proof” method for discerning old from new that is 100% accurate.

Of course, that isn’t the only difference.

Judging By Its Cover

If you compare them both side by side, you’ll notice some distinct differences in style and appearance between the two versions. The contours of the outer casing, the door, display panel, buttons and the like. (Also, there are some important internal differences in mechanical and electronic features. Not readily apparent to the naked eye. But, alas, these are for service personnel’s eyes only!)

Another ‘Tell-Tale’ Sign… Version Number

But, visual differences aside, MIDMARK gives you another clue. A vital piece of numeric (and specific) information to convey to the user just what version of Ultraclave you have.

They use a handy, numeric system that lets you know exactly which one it is.

But to find this “secret code”, you have to look on the back panel of the unit, for the little ID plate that is located there. There, you will find the identifier that is unique and specific to your autoclave. It is the model number with 3-digit version suffix added, and the serial number.

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So, . . .

Which Version Number Are You?

Putting it all together, your complete model/version number will read something like M9-003 or M11-022.

Therein lies another clue to distinguishing the “old” from the “new”, barring the obvious cosmetic differences.

The “older” version numbers end in -001 through -019.

The “newer” version numbers end in -020 and up.

Well, there you have it…

Mystery. Solved!

Now that we’ve figured out which version of Ultraclave you have, . . .

Let us get down to what we came here for.

What DO Those ERROR CODES Mean??

Let’s do the older versions first. Since, after all, they came first.

(Spoiler alert: we will cover the error codes for NEWER version Ultraclaves in our next post, Part 2. Sorry, newbies!)

The older versions had a simple approach to the fine art of error codes. Very few. You could almost count them on two hands. Almost.

There were a grand total of… TWELVE.

Here is a handy list of them for your consideration, with a brief explanation of what each one signifies.


  • E001 – POWER INTERRUPTED (Unit unplugged, or unit shut down unexpectedly.)
  • E002 – CYCLE INTERRUPTED (The STOP button was pushed.)
  • E003 – CYCLE INTERRUPTED (The ON/STANDBY button was pushed.)
  • E004 – DOOR AJAR (Door not fully closed/latched or opened during cycle. Also, possibly a faulty door switch.)
  • E005 – HIGH PRESSURE (Over 35 PSI. Could be due to overloaded chamber, faulty steam trap/bellows, out of calibration.)
  • E006 – HIGH TEMPERATURE (OVER 277℉. Could be due to overloaded chamber, faulty temperature sensor, out of calibration.)
  • E007 – LOW PRESSURE (Unit losing steam through door gasket or one of the internal valves, steam trap or bellows.)
  • E008 – DOOR STUCK CLOSED AT END OF CYCLE (Door did not open automatically due to mechanical or electrical failure.)
  • E009 – PRESSURE DURING DRY CYCLE (This will happen due to residual heat inside chamber if door did not open.)
  • E010, 011, 012 – SOFTWARE ISSUES (Needs PC board replaced or try rebooting unit by unplugging for 30 seconds.)


If you have an older version M9 or M11, I recommend printing this little Table of Errors for reference. It might not “fix” the problem, but at least it will give you an inkling as to what “message of DOOM” or digital cry of help your Ultraclave is sending to you.

[*Note: credit to MEDICANIX for providing the source material for this list.]

Next time: MIDMARK error codes for newer version Ultraclaves!