HEIDENHAIN TNC Error Codes

50: Touch point inaccessible

What it means: During touch probe cycle TCH PROBE 0 (ISO: G55) or a manual probing cycle, the stylus did not reach a touch point within the maximum probing travel set in machine parameter MP6130 (maximum traverse to touch point).^[1][4][3][6]

Control response: probing stops with the message; clear it with CE once the cause is removed

Likely causes

• Touch probe not pre-positioned close enough to the workpiece
• Probing travel in MP6130 too short for the distance to the workpiece

First checks, in this order

1. Pre-position the touch probe nearer to the workpiece and probe again.
2. If the travel really is too short, have the value in MP6130 increased; MP6130 is a machine parameter that the machine tool builder sets.
3. Clear the message with the CE key after fixing the cause.

51: Positioning error

What it means: The servo lag (following error) of a moving axis is greater than the limit in machine parameter MP1710 in lag mode or MP 1410 in feedforward mode.^[1][6]

Also on: Same cause list as error 38 Excessive servo lag in %.2s, which names MP1720 and MP 1420 instead.

Likely causes

• Worn tool
• Machining feed rate too high
• Spindle speed too low
• Not enough lubrication
• Stiff or binding mechanics (HEIDENHAIN: mechanical stiffness)
• Machine vibration
• Hardware fault in the control loop
• Analog axes: too much drift, a defective tachometer or defective carbon brushes

First checks, in this order

1. Replace the worn tool.
2. Reduce the contouring feed rate and increase the spindle speed.
3. Check the lubrication.
4. Remove the cause of stiff or binding movement.
5. Remove any sources of vibration.
6. Analog axes: adjust the drift, replace the tachometer carbon brushes and adjust the tachometer, replace the motor carbon brushes.
7. Inform your service agency.

938: Key non-functional

What it means: The key that was pressed has no function in the current context. The German edition of the list words it as: the key is not allowed in this state or has no function. The correction field of HEIDENHAIN's entry is empty.^[1][6][3]

Likely causes

• A key pressed in an operating mode or screen where it has no function

First checks, in this order

1. Check which operating mode and screen are active, and use the key where it applies.
2. Clear the message with the CE key.

38: Excessive servo lag in %.2s

What it means: The servo lag (following error) of a moving axis is greater than the limit in machine parameter MP1720 in lag mode or MP 1420 in feedforward mode.^[1][6]

Also on: Error 4226 8BD0 Excessive servo lag in %.2s is the drive side message with its own cause list. The German edition of entry 38 lists drive overload, lubrication, binding mechanics, vibration, control loop hardware and a defective analog servo.

Likely causes

• Worn tool
• Machining feed rate too high
• Spindle speed too low
• Not enough lubrication
• Stiff or binding mechanics (HEIDENHAIN: mechanical stiffness)
• Machine vibration
• Hardware fault in the control loop
• Analog axes: too much drift, a defective tachometer or defective carbon brushes

First checks, in this order

1. Replace the worn tool.
2. Reduce the contouring feed rate and increase the spindle speed.
3. Check the lubrication.
4. Remove the cause of stiff or binding movement.
5. Remove any sources of vibration.
6. Analog axes: adjust the drift, replace the tachometer carbon brushes and adjust the tachometer, replace the motor carbon brushes.
7. Inform your service agency if the error occurs frequently.

40: Motion monitoring error in %.2s A

What it means: The axis is moving at least 4 times slower or faster than the nominal speed command output tells it to.^[1]

Likely causes

• Large backlash in the ball screw, gear, belt, coupling or similar
• Worn tool
• Machining feed rate too high
• Spindle speed too low
• Not enough lubrication
• Stiff or binding mechanics
• Machine vibration
• Analog axes: too much drift, a defective tachometer or defective carbon brushes

First checks, in this order

1. Check machine parameter 1140.x.
2. Remove any large backlash.
3. Replace the worn tool.
4. Check the lubrication.
5. Remove the cause of stiff or binding movement.
6. Analog axes: adjust the drift, replace the tachometer carbon brushes and adjust the tachometer, replace the motor carbon brushes.
7. Inform your service agency.

41: Standstill monitoring err. in %.2s

What it means: While the axis should be at a standstill, its position deviation is greater than the value in machine parameter MP1110.x.^[1]

Likely causes

• Analog axes: too much drift
• Vertical axes: weak brake or defective weight balance
• Clamped axes: large mechanical forces during machining

First checks, in this order

1. Analog axes: adjust the drift.
2. Vertical axes: check the brake and the weight balance.
3. Clamped axes: remove the large mechanical forces during machining.
4. Inform your service agency.

43: Dif. in position <> shaft speed too high in %.2s

What it means: The motor is moving while the axis slide is not, or the other way round: the positions worked out from the position encoder pulses and from the speed encoder pulses differ too much.^[1]

Likely causes

• Excessive backlash
• Defective coupling, gear or similar
• Torn belt

First checks, in this order

1. Check MP1144.x.
2. Check the backlash.
3. Repair the defective coupling or gear.
4. Replace the belt.
5. Inform your service agency.

44: MC amplitude too low %.2s

What it means: The amplitude of the encoder signal is too small, or the encoder's contamination signal is active.^[1][6]

Also on: Error 16564 Position encoder %.2s: Amplitude too low covers the same condition; its correction is to check the amplitude of the position encoder signal.

Likely causes

• Encoder contaminated
• Encoder defective
• Moisture has got into the encoder
• Scanning head misaligned (distance, parallelism)
• Encoder cable defective
• Encoder input on the control defective
• Vibration
• Interference signals

First checks, in this order

1. Inform your service agency; that is the only correction HEIDENHAIN gives.
2. Have the items in HEIDENHAIN's cause list checked: encoder cleanliness and moisture, scanning head alignment, encoder cable and the control's encoder input.

45: MC frequency too high %.2s

What it means: The maximum input frequency was exceeded at an encoder input.^[1]

Likely causes

• Fault on the speed encoder signal
• Vibration on the machine

First checks, in this order

1. Check the speed encoder connection, including the ground connection.
2. Check the speed encoder.
3. Check the input frequency of the encoder signal.
4. Eliminate the vibration.
5. Inform your service agency.

46: Position encoder %.2s defective

What it means: Comparing the absolute and the incremental positions of the encoder shows a contradiction.^[1]

Also on: Drive side messages with their own cause lists: 6110 8AF0 Encoder %.2s defective, 8287 AC40 Position encoder %.2s defective, 15697 8C20 Position encoder %.2s defective.

Likely causes

• Absolute and incremental position values of the position encoder do not agree

First checks, in this order

1. Inform your service agency.

52: Stylus already in contact

What it means: The touch probe stylus is already deflected when a probing movement starts.^[1]

Likely causes

• Stylus touching the workpiece or another object at the start of probing
• Damaged touch probe, if the error keeps coming back

First checks, in this order

1. Move the touch probe clear and probe again.
2. If the error recurs often, inspect the probe for damage.
3. If necessary, contact your service agency.

53: Exchange touch probe battery

What it means: The battery in the touch probe is dead.^[1]

Likely causes

• Dead touch probe battery

First checks, in this order

1. Fit a fresh battery.

54: Probe system not ready

What it means: The touch probe system is not ready for probing.^[1]

Also on: Error 1150 Touch probe not ready %.3s has the same causes and corrections.

Likely causes

• Touch probe not connected
• Dead battery in the infrared touch probe
• Transceiver unit contaminated
• Infrared transmission defective or interrupted
• Touch probe interface on the control defective
• Touch probe cable or cable to the transceiver unit defective

First checks, in this order

1. Connect the touch probe.
2. Replace the battery.
3. Clean the infrared window on the touch probe and on the transceiver unit.
4. Check the cabling and replace it if necessary.
5. Inform your service agency.

56: Limit switch %.2s+

What it means: The calculated tool path goes beyond the machine's traversing range set by the software limit switch, or the software limit switch was reached in a manual operating mode. This is the + limit switch message.^[1]

Also on: Error 55 CC limit switch %.2s+ has the same causes and corrections.

Likely causes

• Programmed coordinates outside the traversing range
• Wrong reference point (datum) set
• Axis moved onto the software limit switch in a manual mode

First checks, in this order

1. Check the programmed coordinates and edit the program if required.
2. Check the reference point and set a new one if required.
3. Move the tool in the opposite direction.

58: Limit switch %.2s-

What it means: The calculated tool path goes beyond the machine's traversing range set by the software limit switch, or the software limit switch was reached in a manual operating mode. This is the - limit switch message.^[1]

Also on: Error 57 CC limit switch %.2s- has the same causes and corrections.

Likely causes

• Programmed coordinates outside the traversing range
• Wrong reference point (datum) set
• Axis moved onto the software limit switch in a manual mode

First checks, in this order

1. Check the programmed coordinates and edit the program if required.
2. Check the reference point and set a new one if required.
3. Move the tool in the opposite direction.

59: FN 14: error code %-3u

What it means: A forced error from function FN14 (ISO: D14) in the NC program. When program run or test run reaches the FN14 block, the control stops and shows a message preprogrammed by the machine manufacturer, for example from an OEM cycle.^[1][3]

Also on: Also listed with the text FN 14: Error code %s.

Control response: program run stops at the FN14 block; restart the program after correcting

Likely causes

• The NC program, or a machine manufacturer cycle it calls, reached an FN14 (D14) block

First checks, in this order

1. Look up the error number in the user's manual or machine manual. On the iTNC 530, FN 14 numbers 0 to 299 show as FN 14: Error code with the number, 300 to 999 show a machine-dependent dialog, and 1000 to 1099 are HEIDENHAIN internal messages.
2. Correct the error and restart the program.

62: Ref mark %.2s: incorrect spacing

What it means: During a reference mark run on an encoder with distance-coded reference marks, the axis covered more than 1 000 grating periods without passing a reference mark.^[1]

Likely causes

• Scanning head misaligned (distance, parallelism)
• Encoder contaminated or defective in the area of the reference mark

First checks, in this order

1. Inform your service agency.
2. Have the scanning head alignment and the encoder around the reference mark checked (HEIDENHAIN's listed causes).

63: Handwheel?

What it means: The electronic handwheel is not available to the control.^[1][3]

Likely causes

• Electronic handwheel not connected
• Wrong handwheel selected in machine parameter MP7640
• Transmission line defective
• Handwheel damaged

First checks, in this order

1. Connect the handwheel through the cable adapter.
2. Check machine parameter MP7640.
3. Inspect the transmission line for damage.
4. Inspect the handwheel for damage.
5. Handwheel connectors may only be removed by authorized service personnel; plug the handwheel in before switching on the machine.
6. Inform your service agency.

164: Exchange buffer battery

What it means: The voltage of the buffer battery has dropped below the minimum permissible value. The buffer battery powers the TNC memory so RAM data is not lost when the TNC is switched off.^[1][3]

Likely causes

• Buffer battery run down

First checks, in this order

1. Refer to your machine manual or contact your machine tool builder.
2. On the iTNC 530 the battery is at the back of the MC 422 D; HEIDENHAIN lists 1 lithium battery, type CR 2450N (Renata), ID 315878-01.
3. Switch off the TNC before exchanging the battery; HEIDENHAIN allows only trained service personnel to do it (Caution: Danger of life).

203: EMERGENCY STOP defect

What it means: The internal or external emergency stop circuit is defective.^[1]

Likely causes

• Relays in the chain between the control-is-ready output signal (MC.RDY, STO.A.G) and the control-is-ready acknowledgment (I3, ES.A, ES.B) switch too slowly during the emergency stop or switch-on routine
• Control-is-ready acknowledgment (I3, ES.A, ES.B) short circuited to +24 V

First checks, in this order

1. Check the emergency stop circuit.
2. Check or replace the relays involved in the electrical cabinet.
3. Check or restore the contacts and wiring.
4. Inform your service agency.

205: EMERGENCY STOP PLC

What it means: Emergency stop error message from the machine's PLC; the machine documentation explains it.^[1]

Likely causes

• Condition defined in the machine's PLC program (see the machine documentation)

First checks, in this order

1. Look up the message in the machine documentation.
2. Inform your service agency.

204: TNC temperature too high %d°C

What it means: The temperature sensor finds an excessively high temperature inside the main computer (MC) housing.^[1]

Also on: Error 4905 Processor 1 temperature too high: check heat transfer in the electrical cabinet and the fan on the logic unit.

Likely causes

• Not enough heat dissipation for the MC main computer
• Contaminated filter pads
• Defective climate control unit in the electrical cabinet or operating panel where the MC is installed
• Defective fan
• Defective temperature sensor
• Unfavorable mounting of components

First checks, in this order

1. Clean the filter pads.
2. Check the climate control unit and repair it if necessary.
3. Replace the fan.
4. Inform your service agency.

5236: TNC temperature warning %d°C

What it means: The temperature sensor in the control (MC) finds an excessively high temperature inside the control housing. If the temperature keeps rising, the control hardware may be damaged.^[1]

Likely causes

• Contaminated filter pads
• Defective climate control unit in the electrical cabinet
• Defective fan in the control housing
• Defective temperature sensor

First checks, in this order

1. Check the heat transfer in the electrical cabinet.
2. Check the fan in the control.
3. Clean the filter pads.
4. Repair the climate control unit in the electrical cabinet.
5. Replace the fan, or exchange the control.
6. Inform your service agency.

375: Traverse reference points

What it means: An NC block tried to move an axis that has not yet completed its reference run.^[1]

Likely causes

• Reference run not completed for that axis

First checks, in this order

1. Traverse the reference points (run the reference run), then run the block again.

957: Power interrupted

What it means: The TNC was restarted after a power interruption.^[1]

Control response: acknowledge with CE

Likely causes

• Power interruption

First checks, in this order

1. Acknowledge the power interruption with the CE key.

958: Relay ext. dc voltage missing

What it means: Message after a power interruption: the external dc voltage for the relays is missing.^[1]

Likely causes

• Machine control voltage not switched on yet
• Wiring fault in the electrical cabinet
• Fault in the Machine control voltage ON button

First checks, in this order

1. Switch on the control voltage separately.
2. Check the wiring in the electrical cabinet.
3. Check the 'Machine control voltage ON' button.

2642: Inverter not ready

What it means: The drive cannot be powered on because an inverter is not ready (RDY signal).^[1]

Also on: Error 8225 8A50 Inverter not ready %.2s has the same causes, plus no pulse release because 24 V is missing on terminal X71 or X72 of supply module UV.

Likely causes

• On interface boards for Siemens inverters, the second axis is not enabled
• No switch signals to the inverter contacts or relays
• Compact inverter, inverter supply unit or power module defective
• Interruption in an inverter bus cable (supply bus, unit bus, PWM bus)
• Defective PWM interface on the control

First checks, in this order

1. Remove the interruption in the electrical cabinet.
2. Replace the defective compact inverter, supply unit or power module.
3. Replace the defective cable.
4. Inform your service agency.

11503: 8B40 No drive release %.2s

What it means: The drive for the axis gets no release (enable).^[1]

Likely causes

• Inverter not ready
• No pulse release for the power module
• Uz too high
• Power-fail signal active
• M controls: input I32 inactive; P controls: drive enabling at X50 inactive
• With digital current controller 246 261-xx: illegal motor model selected (for example a linear motor), a Drive on command for an axis that does not exist, or power module not ready when field orientation or current controller adjustment starts (readiness comes through the Ready signal on the PWM cable)

First checks, in this order

1. Inform your service agency.
2. Check the activation and wiring of the pulse release.
3. Check Uz.
4. Check the emergency stop circuit.
5. Non-regenerative system: check that the braking resistor is connected. Regenerative system: check that energy recovery is activated.
6. Check the cable ground and shield.
7. Exchange the power module; with a Siemens inverter, exchange the interface card; exchange the drive control board.

4226: 8BD0 Excessive servo lag in %.2s

What it means: The following error of a moving axis is greater than the limit in machine parameter MP1720.x in lag mode, MP 1420.x in feedforward mode, or MP 1120.x while the commutation angle is calculated.^[1]

Likely causes

• Overloaded drive
• Not enough lubrication
• Stiff or binding mechanics
• Machine vibration
• Hardware fault in the control loop
• Analog axes: servo defective

First checks, in this order

1. Reduce the contouring feed rate and increase the spindle speed.
2. Check the lubrication.
3. Remove the cause of stiff or binding movement.
4. Remove any sources of vibration.
5. Analog axes: check the servo.
6. Inform your service agency if the error occurs frequently.

8004: 8B30 Motor temp. %.2s too high

What it means: The control reports the motor temperature as too high; HEIDENHAIN's causes include a really hot motor as well as sensor, cable and motor table faults.^[1]

Likely causes

• Measured motor temperature really too high
• No temperature sensor
• Motor encoder cable defective (broken wire)
• Incorrect entry in the motor table
• Wrong or defective temperature sensor installed
• Poor contact at the signal connector

First checks, in this order

1. Let the motor cool down.
2. Check the motor encoder cable.
3. Check the entry in the motor table.
4. Measure the temperature sensor.
5. Inform your service agency.

6110: 8AF0 Encoder %.2s defective

What it means: The control reports the encoder of this axis as defective.^[1]

Likely causes

• Scale or scale tape contaminated or defective
• Scanning head contaminated or defective
• Signal cable defective
• Encoder input on the control defective
• Moisture has got in
• Position encoder contaminated
• Motor encoder cable defective
• Motor control board defective

First checks, in this order

1. Inform your service agency.
2. Check the encoder cable.
3. Exchange the position encoder.
4. Exchange the motor control board (HEIDENHAIN adds: or better, the control).

25846: External EMERGENCY STOP

What it means: The PLC input for the control-is-ready signal is inactive, or the emergency stop circuit was interrupted manually or by the control.^[1]

Likely causes

• EMERGENCY STOP button pressed, or the emergency stop circuit interrupted by the control
• Open point in the emergency stop circuit: EMERGENCY STOP button, axis limit switches or wiring

First checks, in this order

1. Release the EMERGENCY STOP button, switch on the control voltage and acknowledge the error message.
2. Check the emergency stop circuit: EMERGENCY STOP button, axis limit switches and wiring.