OKI MB472, MB492 and MB562: Fax Cannot Be Sent or Received — LINE/TEL, Reception Mode and Communication Error

Last Updated on 16.08.2026 by DriverNew

If your OKI MB472, MB492 or MB562 displays Communication Error, does not send a document, or does not receive an incoming fax, the problem is usually not related to the driver. Check the code in the fax journal, the telephone cable connection, the selected reception mode, and the type of telephone line.

This problem is especially common after connecting the MFP to an office PBX, ADSL modem, optical network terminal, or the telephone port of a router. In such cases, normal voice calls may work while fax transmission is interrupted.

Models covered by this guide

This guide applies to the following monochrome MFPs with fax functionality:

• OKI MB472dn, MB472dnw and MB472w;
• OKI MB492dn;
• OKI MB562dnw;
• OKI ES4172LP MFP and ES4192dn MFP;
• OKI ES5162dnw MFP and ES5162LP MFP.

The OKI MB472 uses a button-based control panel. The MB492 and MB562 have a touch panel. Therefore, the paths to some settings are listed separately. The names of individual menu items may also differ slightly depending on the model and firmware version.

Symptoms related to this problem

• after pressing START, the machine does not dial the number;
• the control panel displays Communication Error or Tx Communication Error;
• the MFP redials several times and then cancels the job;
• outgoing faxes work, but incoming faxes are not received;
• an incoming call can be heard on the telephone, but the MFP does not answer;
• the fax is received into memory but is not printed;
• a connection is established, but transmission stops on the first page or one of the following pages;
• the error appeared after connecting the machine to a PBX, router, ADSL modem, or optical network terminal.

Do not change several settings at once. First print the journal and write down the code for the most recent failed operation. Otherwise, it will be difficult to determine which action actually fixed the problem.

Step 1. Print the transmission and reception journal

The journal contains the results of the last 50 fax jobs. If an operation ended with an error, the corresponding row contains a code. An empty cell in the code column means that transmission or reception completed successfully.

OKI MB472

Where the actions are performed: on the MFP button-based control panel.

1. Press the SETTING button.
2. Use the arrow buttons to select Reports and press OK.
3. Select the Fax category and press OK.
4. Select Fax Tx/Fax Rx and press OK.
5. On the confirmation screen, select Yes and press OK.

OKI MB492 and MB562

Where the actions are performed: on the MFP touch panel.

1. Press Device Settings.
2. Press Reports.
3. Select the Fax category.
4. Press Fax Tx/Rx Journal.
5. On the confirmation screen, press Yes.

If the machine asks you to log in as an administrator, enter the current administrator name and password. On a device with unchanged factory credentials, the name is admin and the password is aaaaaa. If the password was changed previously, the factory value will no longer work.

How to understand a code in the fax journal

Find the latest row with the required recipient number and the transmission or reception time. Then compare the code with the following table.

Code	Meaning	What to check
14	Memory is full, fax was not received	Paper, paper jams, and documents stored in memory
21	Line error detected	The telephone line; if the error repeatedly occurs on a working analog line, the MFP fax modem
22, 23	The remote machine did not answer	The number, the condition of the recipient’s line, and the MF(Tone)/DP(Pulse) setting
24, 25	The cable is connected to the wrong port or is not detected	Make sure the incoming line is connected to LINE, not TEL
26	Dial tone is not detected	The PBX Line setting and the connection to the PBX or telephone adapter
27	The line remained busy during redialing	An off-hook handset, a parallel telephone, and the Busy Tone Detection setting
32, 40, 43, 45–47, 49, 52, 60, 66–69, 6a, 82, 83	The connection was interrupted or could not be established in Super G3 mode	Line quality; after completing the other checks, set Super G3 → OFF
48	The recipient’s machine could not receive the fax	Whether the recipient’s fax is ready, has paper, and has enough free memory
4a, 4b	Transmission or reception is blocked by a security function	ID checking and the unwanted fax blocking list
80	An MFP fax modem error was detected	The machine requires service diagnostics
84	Connection timed out	Line quality; reduce the resolution or split a large document
90	Incorrect dialing prefix	The prefix used to access an outside line

A full explanation is available in the OKI fax code table. For initial troubleshooting, the codes listed above are usually sufficient.

Step 2. Check the LINE and TEL connectors

Where the actions are performed: near the telephone connectors on the rear of the MFP. You do not need to turn off the computer.

1. Locate the LINE and TEL connectors on the rear of the machine.
2. Trace where each telephone cable goes.
3. The cable from the wall telephone socket, PBX, ADSL splitter, router, or telephone adapter must be connected to LINE.
4. An external telephone or answering machine must be connected to TEL.
5. Disconnect the plug from LINE and then firmly insert it again. It should lock into place with the retaining clip.
6. Inspect the cable. If the plug is broken or the cable is pinched or damaged, replace it with a working telephone cable of the appropriate type.

Do not connect an external telephone in parallel with the MFP using an ordinary splitter. During transmission, an off-hook handset can interfere with the fax signal or interrupt the connection. Connect one external telephone through the TEL connector. If that telephone also has a built-in fax, disable automatic fax reception on it.

Detailed connection options are shown in the OKI section about connecting the telephone line.

Step 3. Check the telephone line itself

Where the actions are performed: at the wall telephone socket, PBX, or telephone adapter. The MFP control panel is not used yet.

1. Disconnect from the MFP the cable that was connected to LINE.
2. Connect this cable to a working standard telephone.
3. Pick up the handset and check for a continuous dial tone.
4. Make an outgoing voice call.
5. Call this number from another telephone and check the incoming call.
6. After the test, reconnect the same cable to the MFP’s LINE connector.

If there is no dial tone or the voice call is interrupted, troubleshoot the line first. Contact the PBX administrator or telephone service provider. Changing OKI menu settings will not restore a missing telephone signal.

If voice communication works only through a router or separate terminal, the machine is receiving a converted IP telephony signal rather than a direct analog line. In this case, you may later need to disable Super G3.

Step 4. Send a test fax to a known working number

Where the actions are performed: on the MFP control panel. For the test, use one A4 sheet with the word “Test” printed in large letters.

OKI MB472

1. Place the test page in the ADF face up or on the document glass face down.
2. Press the physical FAX button.
3. Select Fax and press OK if the machine displays a fax type selection.
4. Select manual number entry.
5. Enter the full number of a known working fax, including the area code and any required prefix.
6. Check the entered digits and press START.

OKI MB492 and MB562

1. Place the test page in the ADF face up or on the document glass face down.
2. On the touch panel, press Fax/Internet Fax or press the physical FAX button.
3. Press Fax.
4. Press Manual Dial.
5. Enter the recipient’s number and press OK.
6. Press START.

For the first test, do not use a number from the phone book. This eliminates an error in a saved entry. If the machine sends a fax to one number but not another, check whether the recipient’s machine is ready and whether its number is correct.

When sending manually with an external telephone, do not hang up before pressing START. First press START, wait for transmission to begin, and only then end the voice call.

If code 22 or 23 is shown in the journal

Codes 22 and 23 mean that the remote fax did not answer. The cause may be a busy line, an incorrect number, the recipient’s machine being turned off, or an incorrect dialing method.

1. Compare the dialed number with the number provided by the recipient.
2. Make sure an additional digit, such as 0 or 9, is not required to access an outside line.
3. Call the number from a standard telephone and make sure a fax machine answers rather than a voice menu.
4. Wait a few minutes and try sending again: the recipient’s line may have been busy.
5. If the error occurs with every number, check the MF(Tone)/DP(Pulse) setting.

How to check MF(Tone)/DP(Pulse) on OKI MB472

Where the actions are performed: in the administration menu on the MFP button-based control panel.

1. Press SETTING.
2. Select Admin Setup and press OK.
3. Enter the current administrator password, select Enter, and press OK.
4. Select User Install and press OK.
5. Select MF(Tone)/DP(Pulse) and press OK.
6. For a modern push-button telephone line, select Tone.
7. Select Pulse only if the telephone line actually uses pulse dialing.
8. Press OK and return to the main screen.

How to check MF(Tone)/DP(Pulse) on OKI MB492 and MB562

Where the actions are performed: in the administration menu on the MFP touch panel.

1. Press Device Settings.
2. Switch the screen and press Admin Setup.
3. Enter the current administrator name and password and press OK.
4. Press User Install.
5. Press MF(Tone)/DP(Pulse).
6. For a normal modern telephone line, select Tone.
7. Press Back until the main screen appears.

After changing the setting, perform another test transmission and check the journal again. If code 23 appears only when calling one recipient, there is no need to switch the setting back to another value: the problem is most likely on that recipient’s side.

If code 26 is shown in the journal: configure the PBX line

Code 26 means that the machine did not detect a dial tone. This often occurs when it is connected to an office extension, PBX, telephone adapter, or some IP telephony devices.

OKI MB472

Where the actions are performed: in the administration menu on the MFP button-based control panel.

1. Press SETTING.
2. Select Admin Setup and press OK.
3. Enter the current administrator password and confirm the login.
4. Select Fax Setup.
5. Select Fax Settings.
6. Select PBX Line.
7. Set it to Enable and press OK.
8. Return to the main screen and try sending again.

OKI MB492 and MB562

Where the actions are performed: in the administration menu on the MFP touch panel.

1. Press Device Settings.
2. Press Admin Setup and log in.
3. Press Fax Setup.
4. Open Fax Settings.
5. Press PBX Line.
6. Set it to ON.
7. Return to the main screen and send the test page.

If you need to dial 0 or 9 to access an outside line

An office PBX may require a prefix before the public telephone number. Ask the telephone system administrator for the correct prefix. Do not copy the digit from the example: it may be different in your organization.

OKI MB472

Where the actions are performed: in the administration menu on the MFP button-based control panel.

1. Press SETTING.
2. Open Admin Setup and log in.
3. Select Fax Setup.
4. Open Other Settings.
5. Select Prefix.
6. Enter the digit or sequence used to access an outside line.
7. Confirm the value and return to the main screen.

OKI MB492 and MB562

Where the actions are performed: in the administration menu on the MFP touch panel.

1. Press Device Settings.
2. Open Admin Setup and log in.
3. Press Fax Setup.
4. Press Other Settings.
5. Switch the screen and press Prefix.
6. Enter the required digits and press OK.
7. Press Back until the main screen appears.

When dialing manually on the touch panel, the saved prefix is added using the Prefix:N button. Then enter the recipient’s main number. Code 90 indicates that the saved or entered prefix is incorrect.

If code 27 is shown in the journal

First make sure the line is actually free:

1. Hang up the external telephone handset.
2. Disconnect any telephones and splitters connected in parallel.
3. Wait a few minutes and try sending again.
4. If the line is free but code 27 appears every time you dial through a PBX or telephone adapter, temporarily disable busy tone detection.

OKI MB472

Where the actions are performed: SETTING → Admin Setup → User Install → Busy Tone Detection. Set it to OFF.

OKI MB492 and MB562

Where the actions are performed: Device Settings → Admin Setup → User Install → Busy Tone Detection. Set it to OFF.

Do not disable this setting if the machine correctly detects a busy line. After changing it, carefully check the number being dialed: the MFP will no longer be able to use the previous busy signal for normal line status detection.

Step 5. Select the correct reception mode

If outgoing faxes work but incoming faxes are not received, first check Reception Mode. The required option depends on whether the line is used only for fax, shared with a telephone, or shared with an answering machine.

How the line is used	MB472	MB492 and MB562
The line is used only for automatic fax reception	Fax Ready Mode	Fax Ready Mode
One line is shared by a telephone and fax	Tel/Fax Ready Mode	Tel/Fax Ready Mode
An external answering machine is connected to the line	Ans/Fax Ready Mode	Ans/Fax Ready Mode
Calls are normally answered by a person; fax reception is started manually	Tel Ready Mode	Tel Ready Mode
A distinctive ring service is enabled	DRD	DRD

DRD should be selected only when the corresponding telephone company service is enabled. A simple difference in the ringtone melody or volume does not mean that DRD is active on the line.

How to change the reception mode on OKI MB472

Where the actions are performed: in the administration menu on the MFP button-based control panel.

1. Press SETTING.
2. Select Admin Setup and press OK.
3. Enter the current administrator password, select Enter, and press OK.
4. Select User Install and press OK.
5. Select Reception Mode and press OK.
6. Select the appropriate mode from the table above.
7. Press OK and return to the main screen.

How to change the reception mode on OKI MB492 and MB562

Where the actions are performed: in the administration menu on the MFP touch panel.

1. Press Device Settings.
2. Switch the screen and press Admin Setup.
3. Enter the current administrator name and password and press OK.
4. Press User Install.
5. Press Reception Mode.
6. Select the appropriate mode.
7. Press Back until the main screen appears.

If the fax is received but not printed

Where the actions are performed: first near the paper tray and on the MFP control panel, and then, if necessary, in the stored documents menu.

1. Make sure the tray contains paper of the appropriate size.
2. Clear all paper jam messages.
3. Check that the covers are closed and that the tray is fully inserted.
4. For paper used to print received faxes, set the media type to Plain or Recycled. Another media type may prevent automatic tray selection.
5. Print documents stored in confidential boxes or the secure reception area.
6. Delete unnecessary delayed jobs and documents that no longer need to be stored.

Code 14 means that there is not enough free memory for a new fax. Clearing a paper jam and loading paper may automatically free memory because the machine will be able to print pages that have already been received.

If automatic delivery of received faxes to email or a shared folder is enabled, the machine may not print them on paper. In that case, check the automatic delivery setting separately.

Step 6. Disable Super G3 on a poor-quality line or with IP telephony

Super G3 is a high-speed fax communication mode. It is enabled by default and normally works on a good-quality analog line. When transmitting through VoIP, an optical network terminal, some PBXs, or an unstable line, the high-speed mode may fail to negotiate correctly with the remote fax.

Disable Super G3 after checking the cable, number, dialing type, and reception mode. This is especially appropriate for codes 32, 40, 43, 45–47, 49, 52, 60, 66–69, 6a, 82, and 83.

OKI MB472

Where the actions are performed: in the administration menu on the MFP button-based control panel.

1. Press SETTING.
2. Open Admin Setup and enter the current password.
3. Select User Install.
4. Select Super G3.
5. Set it to Disable and press OK.
6. Return to the main screen.

OKI MB492 and MB562

Where the actions are performed: in the administration menu on the MFP touch panel.

1. Press Device Settings.
2. Press Admin Setup and log in.
3. Press User Install.
4. Press Super G3.
5. Set it to OFF.
6. Return to the main screen.

After disabling it, transmission may take longer. This is normal: the machine uses a communication mode that is less demanding on the line. Send a one-page test fax and print a new journal.

Special considerations for ADSL, VoIP, ISDN and optical telephone service

• ADSL: the MFP telephone cable must pass through a working line splitter. Without it, ADSL data can interfere with fax transmission.
• VoIP and optical telephone service: connect the MFP’s LINE connector to the analog telephone output of the router, optical network terminal, or adapter. The Ethernet connector is not used for this.
• Office PBX: connect the extension line to LINE, enable PBX Line, and save an outside-line prefix if necessary.
• ISDN: the MFP cannot be connected directly to a digital ISDN line. A terminal adapter with an analog telephone output is required.

Test reception from another fax machine

Where the actions are performed: on another working fax machine or using a service that can send a test fax to your number.

1. Set the OKI to automatic fax reception mode.
2. Make sure the machine is turned on, there are no errors on the control panel, and paper is loaded in the tray.
3. Send one page to the OKI number.
4. Check whether the call arrives and whether the MFP answers.
5. If the machine answers but transmission is interrupted, print the Fax Tx/Rx Journal and check the new code.
6. If the call does not arrive at all, check the number, the line, the service provider’s equipment, and incoming call routing in the PBX.

If incoming faxes fail only from one sender, ask that sender to resend the document at a lower resolution. It is also useful to test transmission from another fax machine: this helps distinguish an OKI problem from incompatibility or an error on the side of a particular sender.

When to contact the telephone service provider or a service center

Contact the telephone service provider or PBX administrator if:

• there is no dial tone on the test telephone;
• voice calls are interrupted or contain severe noise;
• incoming calls do not reach the connector to which the MFP is connected;
• faxing fails only through VoIP, a router, or an optical network terminal;
• the outside-line prefix, dialing rules, or purpose of the extension line are unknown.

The MFP itself requires diagnostics if code 80 repeatedly appears or if the machine does not detect a working analog line after it has been tested with another telephone. Before contacting service, write down the model, the code from the journal, how the line is connected, and the result of the test call. This information will help distinguish a fax modem fault from a telephone network problem.