Okuma Alarm Codes

Alarm 0721: DeviceNet error

What it means: The DeviceNet I/O network reported an error, so the NC lost normal contact with one or more I/O slave stations.^[1][3][10]

Likely causes

• Poor electrical connection on the DeviceNet network or its network power supply
• Wrong switch settings on a slave station, for example a duplicate MacID
• I/O mapping missing for an option or software that was just installed (Okuma sees this most on GENOS lathes when the extra DVD with the I/O mapping software was not installed)
• Hardware or software failure, as the manual lists

First checks, in this order

1. Write down the alarm code: the first two hex digits are the MacID of the slave station, the next two its status, for example 46 duplicate MacID, 5B bus off, 5C network power supply off
2. Check the network power supply, cables and connectors at that slave station
3. If the alarm started right after adding an option or loading software, check the I/O mapping (on GENOS lathes, that the I/O mapping DVD was installed)
4. Check the station switch settings before replacing hardware

Alarm 0750: The spec.-code or select-soft. was wrong

What it means: The NC software and the PLC software do not match, or the combination of specification codes is wrong.^[1][10]

Likely causes

• Specification code set wrongly
• Wrong PLC software version selected

First checks, in this order

1. Note what changed last, such as a software load, an option install or a board swap
2. Compare the specification codes with the machine's specification
3. Check that the selected PLC software version matches the NC software
4. Call Okuma service if the codes and versions look right

Alarm 0757: MF-SAFETY Error

What it means: The MF-SAFETY safety controller detected an abnormality.^[1][10]

Likely causes

• MF-SAFETY unit failure
• Wrong MF-SAFETY mode setting or NC operation mode setting
• MFU I/O unit failure
• Error in the MF-SAFETY software (safety logic)

First checks, in this order

1. Write down the alarm code shown with the alarm
2. Check the MF-SAFETY mode setting: the manual's measure is to turn all MF-SAFETY switches (SW1) to OFF
3. Then suspect the MFU I/O unit and the MF-SAFETY unit, which the manual says to replace
4. Corrections to the safety logic software are a job for Okuma service

Alarm 0758: Safety I/O Error

What it means: MF-SAFETY found an error in the safety I/O link (SIO link) communication or in a safety input or output.^{[1][3][4][10]}

Likely causes

• A shorted solenoid, or a switch exposed to coolant that shorted out, which can also damage an I/O board (Okuma support)
• Faulty SIO-link cable
• Faulty MFU I/O unit or another unit connected to the SIO link
• Faulty MF-SAFETY unit or a wrong IO data coupling file

First checks, in this order

1. Write down the alarm code: Okuma says the code that follows the alarm usually points to the input or output location, although finding the slot or connector can take deeper troubleshooting
2. Inspect the safety switches, solenoids and connectors on that circuit for coolant and shorts
3. Check and replace the SIO-link cable
4. Then replace the MFU I/O unit, the unit on the SIO link or MF-SAFETY, as the manual lists

Alarm 0759: Safety Servo Link Error

What it means: An error occurred in the safety communication over the servo link between MF-SAFETY and the axis drives.^[1][10]

Likely causes

• Servo link cable or connector fault
• Faulty MF-SAFETY unit
• Faulty unit connected to the servo link
• Wrong axis ID configuration data file

First checks, in this order

1. Write down the alarm code: in several codes the XX digits give the axis ID of the problem axis
2. Check the servo link cable and connectors for that axis
3. If a drive, axis or option was changed recently, check the axis ID configuration data file
4. Then replace the unit on the servo link or MF-SAFETY, as the manual lists

Alarm 0812: MCS Servo link start

What it means: At power on, the NC failed to initialize the MCS servo and spindle drive system over its serial servo link (titled MCS start on OSP-E100M and MCS initialization error on P300L lists).^[1][2][3][4]

Likely causes

• Faulty inverter (drive) unit
• Wrong controller ID number set in an MCS unit
• Specification code setting error
• Wrong connection in the MCS serial link, sometimes left over from earlier troubleshooting (Okuma support)

First checks, in this order

1. Check the LED display on each inverter unit, as the manual directs
2. Check the ID number (address) settings, especially on any drive that was just swapped
3. Check the servo link cable routing and connectors against the original wiring
4. Check the specification code, then call Okuma service if everything above is right

Alarm 0813: MCS Servo link communication error

What it means: At power on, communication with the MCS drives failed on the servo link (titled MCS communication error on OSP-E100M and P300L lists).^[1][2][4]

Likely causes

• Faulty inverter unit
• MCS connection error or a faulty MCS connection cable
• FCP board (named on OSP-E100M)
• Software fault

First checks, in this order

1. If servo link information appears in the middle of the screen, read it: the manual says to judge the cause from that message
2. Open the cabinet and check the LEDs of every MCS unit on the failing channel; the manual says normal units show 22
3. Check the servo link cable and connectors on that channel
4. Replace the inverter unit that does not show the normal state

Alarm 0945: Memory board / battery life

What it means: The backup battery has reached the end of its life; OSP-E100M names the memory board battery, and Okuma says on OSP-P500 it is the UPS battery, which lasts about six years.^{[2][3][4][10]}

Likely causes

• Memory board battery past its service life (OSP-E100M)
• UPS battery at the end of its life, about six years (OSP-P500, Okuma support)

First checks, in this order

1. Change the battery right away: Okuma warns that if the battery reaches its end of life all parameters in the control could be lost
2. Have parameter and program backups ready, since the OSP-E100M measure is to change the battery and reinstall the software and user data
3. On OSP-P500, Okuma also advises changing the coin battery on the HMI/PNC board, which keeps date and time, at the same time

Alarm 1071: Memory board / battery hurry exchange

What it means: The memory board battery has finished its service life and must be replaced quickly (P300L lists: Memory board battery depleted. Replace quickly!).^[2][4][11]

Likely causes

• Memory board battery past its service life

First checks, in this order

1. Back up programs and parameters first, because a depleted memory board battery puts parameters and system memory at risk
2. Change the memory board battery, as the manual directs
3. If data was lost, reload software and user data from the backup (the OSP-E100M measure for the related battery alarms 0945 and 4035)

Alarm 1151: MCS Exception processing

What it means: A fatal fault occurred inside an MCS inverter (drive) unit or its software; Okuma support calls it MCS inverter unit detected an error and P300L lists call it MCS Inverter unit fault.^[1][2][3][4]

Also on: ['0851 (P)', '2151 (B)', '3151 (C)', '4151 (D)']

Likely causes

• Defective inverter control board
• Motor overcurrent or a shorted motor, which can also take out the drive unit
• Low or high voltage, or a control power supply or encoder power supply fault
• Damaged encoder cable at the motor (in one Okuma case this led to replacing the inverter, MCS power supply and servo controller)

First checks, in this order

1. Read the character string #number: #1 control board, #2, #10 and #11 control power supply, #8 magnetic encoder power supply, #9 encoder power supply, #12 to #14 gate signal, inverter bridge and motor overcurrent
2. For #8 or #9 check the encoder and its cable before the drive
3. For #14, insulation test the motor and its power cable with the cable off the drive
4. Check the motor before fitting a new drive, because Okuma has seen a faulty motor take out a whole drive unit

Alarm 1156: MCS DC-bus voltage alarm

What it means: The DC bus voltage inside an inverter unit rose or fell abnormally, so the drive cannot supply current to the motor.^[1][2]

Also on: ['0856 (P)', '2156 (B)']

Likely causes

• Supply voltage out of range or a momentary power interruption
• Power supply unit fault (the OSP-E100M list names it for a voltage rise)
• Inverter unit fault

First checks, in this order

1. Read the code: on OSP-E100M the first four hex digits are the detected overvoltage and the last four the undervoltage, in 15.3 mV steps
2. Measure the incoming supply and look for dips or short outages at the time of the alarm
3. Check the power supply unit, then the inverter unit of the axis shown

Alarm 1157: MCS Motor over current

What it means: The inverter unit detected overcurrent in the motor power line.^[1][2]

Also on: ['0857 (P)', '2157 (B)']

Likely causes

• Motor insulation failure
• Inverter unit fault

First checks, in this order

1. Read the code: it holds the U-phase and W-phase currents measured when the alarm tripped
2. Disconnect the motor power cable at the drive and insulation test the motor and the cable
3. If insulation is good, suspect the inverter unit

Alarm 1158: MCS Power unit over heat

What it means: The temperature of the inverter unit rose abnormally.^[1][2]

Likely causes

• Heavy operating conditions or overload operation
• Inverter unit fault

First checks, in this order

1. Review the duty on the axis or spindle shown, such as heavy cuts or frequent starts and stops
2. Look in the alarm history for drive or power supply unit cooling fan alarms (the P300 list has them as 4145, 4147, 4148 and 4149)
3. If it repeats under normal load, replace the inverter unit

Alarm 1160: MCS Supply voltage flutter

What it means: The input voltage to the MCS power supply unit rose or dropped abnormally, so the machine cannot hold the voltage it needs to run.^[1][2][3]

Also on: ['0860 (P)', '2160 (B)', '3160 (C)', '4160 (D)']

Likely causes

• Plant supply voltage too low or too high, or a momentary power interruption
• Power cable too thin or too long for the machine
• Loose connection on the power lines
• Power supply unit fault

First checks, in this order

1. Note when it happens: Okuma says it shows most often during heavy spindle acceleration or deceleration, when the machine draws the most power
2. Read the code: it is the voltage at detection in hex, where 01 is 0 V and 80 is 300 V
3. Check that the supply is sized to the machine kVA rating and tighten the power line connections
4. Check the power cable size and length, then the power supply unit

Alarm 1163: MCS Encoder-link error

What it means: Communication with an encoder over the encoder link failed.^[1][2]

Likely causes

• Motor encoder, ABSO SCALE, shaft encoder or independent encoder of the axis shown
• Encoder link cable or connector
• Inverter unit control board

First checks, in this order

1. Read the code: on OSP-E100M the YY digits tell which device, 00 motor encoder, 01 shaft encoder, 02 independent encoder, 03 ABSO SCALE
2. Check that device's encoder link cable and connectors
3. If the cable is good, replace the encoder, then the inverter control board

Alarm 1164: MCS Encoder error

What it means: The motor encoder could not detect position data.^[1][2]

Likely causes

• Faulty motor encoder
• Multi-turn position data outside the allowed range (the code then shows XX as 0 and YY as 1)

First checks, in this order

1. Read the code: XX is the encoder error code, YY the encoder status, ZZZZ the multi-turn data
2. Check the encoder connector and cable first, even though the manual lists only the encoder
3. Replace the motor encoder of the axis shown

Alarm 1173: MCS Motor over heat

What it means: The temperature of the motor rose abnormally.^[1][2]

Likely causes

• Operating conditions, such as starting and stopping CW and CCW at high frequency
• Spindle motor fan not working or a dirty heat sink (named for VAC motors on OSP-E100M)
• Faulty motor, or a faulty motor encoder, which senses the temperature on BL motors
• Encoder link cable fault

First checks, in this order

1. Read the code (OSP-P300): 0010 overheat, 0011 motor overheat, 0012 encoder overheat, 0013 motor and encoder overheat
2. Check whether the motor is really hot; if it is, check its fan, heat sink and the duty cycle
3. If the motor is cool, suspect the motor encoder and the encoder link cable

Alarm 1174: MCS Servo-link error

What it means: A communication error occurred on the servo link, so the drive cannot receive commands from the NC.^[1][2]

Also on: ['0874 (P)', '2174 (B)', '3174 (C)', '4174 (D)']

Likely causes

• Servo link cable or connector
• Inverter unit control board
• SVDN board

First checks, in this order

1. Read the code bits: for example bit 8 wire breakage, bit 5 CRC error, bit 0 time-out
2. Check the servo link cable and connectors at the axis shown
3. Then the inverter control board and the SVDN board

Alarm 1181: MCS DIFF over

What it means: The following error (the gap between the calculated position and the actual position) grew past the allowed value, so the axis could not go where it was commanded.^[1][2][3]

Also on: ['0881 (P)', '2181 (B)', '3181 (C)', '4181 (D)']

Likely causes

• Mechanical drag or resistance, such as a faulty ball screw or bearing, chip buildup, broken tools or defective parts
• Damaged servo amplifier (inverter unit), cable or motor
• Servo data file (named on OSP-E100M)

First checks, in this order

1. Do not just press reset and carry on: Okuma says to find and remove the root cause first
2. Look for chips, a crash, a broken tool or a jam on the axis shown
3. Check that the axis moves freely: ball screw, bearings and ways come first in the manual's list
4. If the mechanics are free, check the motor, its cable and the inverter unit

Alarm 1186: MCS Collision detected

What it means: The NC torque limiter detected an axis collision from the relation between motor output torque and motor acceleration.^[1][2]

Likely causes

• A real collision or interference in the mechanical drive
• Wrong NC torque limiter setting value
• Faulty motor encoder
• Faulty inverter unit or motor

First checks, in this order

1. Inspect the axis shown, the tool, the workpiece and the fixture for a crash
2. Check the program and offsets that ran just before the alarm
3. If there was no collision, check the NC torque limiter setting
4. Then check the motor encoder, inverter unit and motor

Alarm 1192: MCS Motor over load

What it means: The motor load exceeded the preset value and the overload protection tripped.^[1][2]

Likely causes

• Overload from machine operation, such as heavy cuts
• Faulty motor
• Wrong servo data file

First checks, in this order

1. Review the cut and the duty on the axis or spindle shown
2. Check that axis for mechanical drag
3. If the code is FFFFFFFF, the motor could not be identified when the electronic thermal started, so check the servo data
4. Then check the motor

Alarm 1257: Emergency stop

What it means: The emergency stop button is pressed, or the power was turned on with it pressed (machining center numbering; OSP lathe lists show Emergency stop as 1700).^{[1][2][8][11]}

Also on: ['1700 (OSP-P300L lathe lists)', '1701 (OSP-E100M)']

Likely causes

• Emergency stop button pressed
• Power turned on while the button was still pressed

First checks, in this order

1. Find out why the button was pressed and remove that cause
2. Release (reset) the emergency stop button
3. Press the CONTROL ON button again, as the manual directs

Alarm 2160: MCS Supply voltage flutter

What it means: The same fault as 1160, the input voltage to the power supply unit rose or dropped abnormally, reported at Alarm B level so the active block finishes before the machine stops.^[1][2][3]

Likely causes

• Supply voltage sagging during heavy spindle acceleration or deceleration (Okuma support)
• Supply not sized to the machine kVA rating
• Loose power line connection, or a power cable that is too thin or too long
• Power supply unit fault or a momentary power interruption

First checks, in this order

1. Note whether it comes during spindle acceleration or deceleration
2. Check the supply against the machine kVA rating, as Okuma advises
3. Inspect and tighten the power line connections
4. Then check the power supply unit

Alarm 2181: MCS DIFF over

What it means: The same fault as 1181, the axis following error exceeded the allowed value, reported at Alarm B level so the active block finishes first.^[1][2]

Likely causes

• Overload from a faulty ball screw or bearing
• Faulty motor
• Faulty inverter unit
• Servo data file

First checks, in this order

1. Check the axis shown for chips, crash damage and drag
2. Check that it moves freely through its travel
3. Then check the motor, its cable and the inverter unit

Alarm 2228: Unusable M code

What it means: An M code was programmed that cannot be used in the current mode or block (machining center numbering; OSP lathe lists use 2228 for a different alarm).^[1][2][4]

Likely causes

• On OSP-E100M: M396 to M399 given outside synchronized tapping mode
• On OSP-P300M (code 1): M346 or M347 placed in the same block after a reference to system variable VPLT or VNLT

First checks, in this order

1. Read the code: on OSP-E100M it is the M code in hex
2. Check that M code against the machine's M code list and the active mode
3. Move it to its own block or into the right mode, as the manual's measures say

Alarm 2236: Program end code not found

What it means: The control did not find the end of program code at the end of the program.^[1][2][4]

Likely causes

• No end of program code at the end of the program (code 1)
• A left parenthesis with no matching right parenthesis (code 2)
• No G40 to cancel cutter radius compensation (code 3)

First checks, in this order

1. Read the code number shown with the alarm
2. Add the end of program code (M02 or M30) as the last block
3. Check for an unclosed parenthesis or a missing G40, then run again

Alarm 2268: Plus travel limit over

What it means: A target position in the program is beyond the positive travel limit of the axis shown (machining center numbering, where 2269 is Minus travel limit over; OSP lathe lists use 2268 for a different alarm).^[1][2][4]

Likely causes

• Wrong command value in the program
• Travel end limit values in the system or user parameters wrong or not set
• Home position system parameter wrong or not set

First checks, in this order

1. Read the axis shown and the code (OSP-E100M lists each case, for example 2 for cutting feed and 6 for rapid feed)
2. Check the command value in that block against the axis travel
3. If the program is right, check the travel limit and home position parameters

Alarm 2299: Cutter radius comp.: no intersecting point

What it means: With cutter radius compensation on, the control could not find an intersection point between the paths of two blocks (machining center numbering).^[1][2]

Likely causes

• Program error at the corner or arc given by the code
• Wrong cutter radius compensation data

First checks, in this order

1. Read the code: 200 outside obtuse angle cut, 300 inside cut, 400 circular cut or compensation in the reverse direction
2. Check the program at that pair of blocks
3. Check the cutter radius compensation value for the tool

Alarm 3261: Tool life management No spare tool

What it means: On OSP lathe lists, a tool group has run out of spare tools to index automatically within the group (machining centers show this as 3277).^[1][6][12]

Likely causes

• Every tool in the group has reached its life
• No spare tool registered in the group

First checks, in this order

1. Replace the worn tools in that group
2. Reset their life count on the tool life screen and set them back to OK
3. As Alarm C the running program finishes, but a new one cannot start until the alarm is released

Alarm 3276: Cycle time over

What it means: One cycle, from cycle start to M02 or M30, took longer than the time set in the parameter (machining center numbering; 1302 is the Alarm A version).^[1][2]

Likely causes

• The cycle ran longer than the set limit
• Limit parameter set too short for the program

First checks, in this order

1. Compare the real cycle time with the limit parameter
2. Look for waits or stops during the cycle
3. If the cycle is normal, set a limit that fits the program

Alarm 3277: Tool life management no spare tool

What it means: The active tool became an NG tool but its tool group has no registered spare (OK) tool (machining center numbering).^[1][2]

Likely causes

• The tool reached its life with no spare left in the group
• Spare tool not registered in the tool group

First checks, in this order

1. Read the code: it is the tool group number of the tool that ran out
2. Replace the tools in that group with new ones
3. Set the life quantities and set OK/NG back to OK: on P200M/MA in the tool management screen, on P300S/M in the tool life sheet (SET and LEFT)

Alarm 4035: Memory board / battery change

What it means: The memory board battery must be changed because its life is ending (P300L wording: Replace memory board battery).^[2][9]

Likely causes

• Memory board battery at the end of its service life

First checks, in this order

1. Do not turn the power off: the manual says to call Okuma without switching off
2. Back up programs and parameters
3. Have the battery changed; the OSP-E100M measure includes reinstalling the software and user data afterwards

Alarm 4057: Battery life

What it means: On OSP-P300 lathe lists, the UPS battery and the coin battery are at the end of their life.^[3][5][13]

Likely causes

• UPS battery past its life (Okuma gives about six years for the OSP-P500 UPS battery)
• Coin battery past its life (on OSP-P500 it backs up the date and time on the HMI/PNC board)

First checks, in this order

1. Plan the change now: as Alarm D it does not stop the machine, but Okuma warns for OSP-P500 that a UPS battery left to reach its end of life can lose all parameters
2. Back up parameters and programs
3. Change the UPS battery and the coin battery together

Alarm 4085: Fan motor error on panel computer unit

What it means: A cooling fan in the panel computer (the CPU fan or the power supply fan, per Okuma) is turning outside its specified speed range.^[1][3][13]

Likely causes

• Panel computer cooling fan worn or failing
• Fan not plugged in correctly

First checks, in this order

1. Look at the fans: are they plugged in correctly and turning at normal speed
2. Replace a fan that turns slowly or not at all; the manual warns the life of the unit may be shortened
3. If the fans run at the right speed, have the panel computer itself inspected

Alarm 4086: UPS is not functioning

What it means: The UPS in the panel computer power unit is not working, so the CNC may not shut down properly in a power outage.^[1][4]

Likely causes

• UPS battery not charged enough
• UPS battery past its life
• Fault in the panel computer power circuit

First checks, in this order

1. Check the lamp on the power unit of the panel computer
2. If the battery is discharged, turn on the main breaker and leave it on to charge the battery
3. If the battery life is over, change the UPS battery

Alarm 4122: Maintenance be necessary

What it means: A maintenance item has passed its advance notice time (P300L lists: Maintenance (by user) necessary, the count passed the caution time on the user maintenance monitor).^[1][4]

Likely causes

• A scheduled maintenance item is due
• The completion date was not entered after the work was done

First checks, in this order

1. Read the code: it is the item number whose notice time has passed
2. Do the maintenance for that item
3. Enter the date the work was done for that item number, as the manual directs

Alarm 4141: MCS Please push reset button for spindle stop

What it means: The front door stays locked because the spindle is turning; press Reset to stop the spindle.^[1][13]

Likely causes

• Door opening requested while the spindle is still rotating

First checks, in this order

1. Press the Reset button to stop the spindle
2. Wait until the spindle has stopped, then open the door

Alarm 4249: Tool life warning

What it means: On OSP lathe lists, the life (in number of workpieces) of the last tool in a tool group has reached the set warning number.^[7][13]

Likely causes

• The last tool in the group is close to its life count
• Warning count set to give early notice

First checks, in this order

1. Get a replacement tool ready for that group
2. Check the tool life settings for the group
3. Change the tool in time: once the last tool's life is used up the group has no spare left, and 3261 can follow