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

Last Updated on 28.08.2026 by DriverNew

If an OKI MB472, MB492 or MB562 displays “Communication error”, does not send a document or does not receive an incoming fax, the cause is usually not the driver. You need to check the code in the fax log, the telephone cable connection, the selected reception mode and the telephone line type.

The problem occurs especially often after the MFP is connected to an office PBX, ADSL modem, optical network terminal or a router’s telephone socket. 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 capability:

• 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 operator panel. The MB492 and MB562 have a touch panel. Therefore, the paths to some settings are provided separately. The names of individual items may also vary slightly depending on the model and firmware version.

Symptoms related to this fault

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

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

Step 1. Print the transmission and reception log

The log contains the results of the latest 50 fax jobs. If an operation ended with an error, a code is shown in the corresponding row. A blank cell in the code column means that transmission or reception was completed successfully.

OKI MB472

Where to perform the actions: on the MFP’s button-based operator panel.

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

OKI MB492 and MB562

Where to perform the actions: on the MFP’s touch panel.

1. Press Device Settings.
2. Press Reports.
3. Select the Fax category.
4. Press Fax Tx/Rx Log.
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. A machine with unchanged factory credentials uses the name admin and the password aaaaaa. If the password was changed previously, the factory default will no longer work.

How to interpret a code in the fax log

Find the most recent row with the relevant recipient number and transmission or reception time. Then compare the code with the following table.

Code	Meaning	What to check
14	Memory is full; the fax was not received	Paper, paper jams and documents stored in memory
21	A line error was detected	The telephone line; if the error repeats on a working analog line, the MFP’s fax modem
22, 23	The remote machine did not answer	The number, the recipient’s line status and the MF (Tone)/DP (Pulse) setting
24, 25	The cable is connected to the wrong connector or is not detected	Whether the incoming line is connected to LINE, not TEL
26	The dial tone is not detected	The PBX Line setting and the connection to a 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 and has paper and free memory
4a, 4b	Transmission or reception was blocked by a security function	ID checking and the Block Junk Fax list
80	An error was detected in the MFP’s fax modem	The machine requires service diagnostics
84	The communication time limit expired	Line quality; lower the resolution or split a large document
90	The dialing prefix is incorrect	The outside-line access prefix

Step 2. Check the LINE and TEL connectors

Where to perform the actions: near the telephone connectors on the back of the MFP. You do not need to turn off the computer.

1. Find the LINE and TEL connectors on the back 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. Remove the plug from LINE and insert it firmly again. The locking tab must click into place.
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 through an ordinary splitter. During transmission, an off-hook handset can distort the fax signal or interrupt the connection. Connect one external telephone through the TEL connector. If that telephone also has a built-in fax, turn off automatic fax reception on it.

Step 3. Check the telephone line itself

Where to perform the actions: at the wall telephone socket, PBX or telephone adapter. The MFP’s operator 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, fix the line fault first. Contact the PBX administrator or telephone service provider. Changing the 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. You may need to turn off Super G3 later.

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

Where to perform the actions: on the MFP’s operator panel. For the test, use one A4 page with the word “Test” printed in large letters.

OKI MB472

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

OKI MB492 and MB562

1. Place the test page face up in the ADF or face down on the document glass.
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 then press OK.
6. Press START.

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

When transmitting manually with an external telephone, do not put down the handset before pressing START. First press START, wait for transmission to begin and only then end the voice call.

If code 22 or 23 appears in the log

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 the wrong dialing method.

1. Compare the number you dialed with the number provided by the recipient.
2. Make sure that an additional digit, such as 0 or 9, is not required to access an outside line.
3. Call this number from a standard telephone and make sure a fax answers, not a voice menu.
4. Wait a few minutes and send 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 the OKI MB472

Where to perform the actions: in the administrative menu on the MFP’s button-based operator panel.

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

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

Where to perform the actions: in the administrative menu on the MFP’s touch panel.

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

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

If code 26 appears in the log: 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, private branch exchange, telephone adapter or some IP telephony devices.

OKI MB472

Where to perform the actions: in the administrative menu on the MFP’s button-based operator panel.

1. Press SETTING.
2. Select Admin Setup, and then press OK.
3. Enter the current administrator password and confirm the login.
4. Select Fax Setup.
5. Select Fax Setting.
6. Select PBX Line.
7. Set it to ON, and then press OK.
8. Return to the top screen and send again.

OKI MB492 and MB562

Where to perform the actions: in the administrative menu on the MFP’s touch panel.

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

If 0 or 9 is required to access an outside line

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

OKI MB472

Where to perform the actions: in the administrative menu on the MFP’s button-based operator 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 top screen.

OKI MB492 and MB562

Where to perform the actions: in the administrative menu on the MFP’s 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 then press Prefix.
6. Enter the required digits, and then press OK.
7. Press Back until the home screen is displayed.

When dialing manually on the touch panel, the saved prefix is added with the PreFix:N button. After pressing it, enter the recipient’s main number. Code 90 indicates that the saved or entered prefix is incorrect.

If code 27 appears in the log

First, make sure that the line is actually free:

1. Put down the handset of the external telephone.
2. Disconnect any telephones and splitters connected in parallel.
3. Wait a few minutes and send again.
4. If the line is free but code 27 appears every time you dial through a PBX or telephone adapter, temporarily turn off busy tone detection.

OKI MB472

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

OKI MB492 and MB562

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

Do not turn off 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 tone to determine the line status normally.

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 faxing, 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 used for telephone calls and faxes	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 usually answered by a person; fax reception is started manually	Tel Ready Mode	Tel Ready Mode
A distinctive ring service is enabled	DRD	DRD

Select DRD only if the corresponding telephone company service is enabled. A normal difference in ring melody or volume does not mean that DRD is operating on the line.

How to change the reception mode on the OKI MB472

Where to perform the actions: in the administrative menu on the MFP’s button-based operator panel.

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

How to change the reception mode on the OKI MB492 and MB562

Where to perform the actions: in the administrative menu on the MFP’s touch panel.

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

If the fax is received but not printed

Where to perform the actions: first near the tray and on the MFP’s operator panel, then, if necessary, in the menu for stored documents.

1. Make sure that the tray contains paper of an appropriate size.
2. Clear all paper jam messages.
3. Check that the covers are closed and the tray is fully inserted.
4. For paper intended for printing received faxes, set the type to Plain or Recycled. Another media type may prevent the tray from being selected automatically.
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 free memory automatically because the machine will be able to print pages that have already been received.

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

Step 6. Turn off Super G3 for a poor line or IP telephony

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

Turn off 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 to perform the actions: in the administrative menu on the MFP’s button-based operator 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 OFF, and then press OK.
6. Return to the top screen.

OKI MB492 and MB562

Where to perform the actions: in the administrative menu on the MFP’s 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 home screen.

After it is turned off, 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 log.

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

• ADSL: the MFP’s telephone cable must pass through a working line splitter. Without it, ADSL data may interfere with the fax signal.
• 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 port is not used for this.
• Office PBX: connect the extension line to LINE, enable PBX Line and, if necessary, save the outside-line access prefix.
• ISDN: the MFP cannot be connected directly to a digital ISDN line. A terminal adapter with an analog telephone output is required.

Check reception from another fax

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

1. Set the OKI to an automatic fax reception mode.
2. Make sure that the machine is turned on, there are no errors on the operator panel and the tray contains paper.
3. Send one page to the OKI number.
4. Check whether a call arrives and whether the MFP answers.
5. If the machine answers but transmission stops, print the Fax Tx/Rx Log and check the new code.
6. If no call arrives at all, check the number, line, provider 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 fault from an incompatibility or error on one sender’s side.

When help from the telephone provider or a service center is required

Contact the telephone service provider or PBX administrator if:

• there is no dial tone on the telephone used for testing;
• voice calls are interrupted or affected by heavy 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 access prefix, dialing rules or purpose of the extension line is unknown.

The MFP itself requires diagnostics if code 80 appears repeatedly or if the machine does not detect a working analog line after it has been tested with another telephone. Before requesting service, write down the model, the code from the log, 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.