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Occasional Contributor
Posts: 7
Registered: ‎10-09-2019

Two problems during scanning (Codes 2, 156, 50 and Codes  2, 140, 21) on Canon G7040

I have Canon G7040 attached to Windows 10 x64 via USB cable. Today I have scanned massive document, contained hundred od pages, via automated loader at the top of my device (they called it ATF, if I am right).


After each several pages (from 3 to 15, it depends) I got one of two errors - with codes Code 2, 156, 50 or with Codes  2, 140, 21. It seems it is connectivitu problem. Canon ScanGear software also is freezed during scanning, and I had to switch off/on the printer. 


Are there any ways how to solve it?


Esteemed Contributor
Posts: 3,378
Registered: ‎11-19-2017

Re: Two problems during scanning (Codes 2, 156, 50 and Codes  2, 140, 21) on Canon G7040


The "automatic loader" is actually the ADF (Automatic Document Feeder)


Your errors appear to indicate a communications issue between your PC and scanner.  It might be the cable, but is more likely a software issue.


You did not say if this is a new issue or something that has happened due to update or upgrade.  System changes, etc.


I would suggest downloading the latest version of the printer drivers from your product.  There are several builds of Windows 10 available, (we don't know what version or build you are running) yours may also be different since your product is intended for the EU.


PIXMA G7040 - Canon Europe (


Uninstalling and reinstaling the printer and its software with restart inbetween might help.  3rd party antivirus and firewall software can also cause communication issues.

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Occasional Contributor
Posts: 7
Registered: ‎10-09-2019

Re: Two problems during scanning (Codes 2, 156, 50 and Codes  2, 140, 21) on Canon G7040



No system changes. I use Windows x10 20H2 OS Build 19042.685, it should be the latest one.


It is a new issue for me, but I scanned 3-5 pages previously. I had never scanned 500 pages before, and may be reason was buffer overfilling (it is my hypothesis, I do not know exactly).


My device is connected my USB cable desktop PC, and Wi-Fi is also activated, because I like possibility to send something from my IPHone for printing. So, my second hypothesis is two connection types (Wi-Fi and USB) can interfere and led to problems.


To tell the truth, I remember similar problem (2,157, 50), see the OLD screenshot. I obtained it when my printer was connected to another device (laptop) via Wi-Fi, but then I reconnected to Desktop via USB and the problem dissapered. Wi-Fi signal is not very strong, 70% usually (measured by the printer itself).



Thanks for the link to drivers, I will reinstall. It will take some time. Then I wiill check scanning it post a reply here.


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