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ControlLogix PLC Minor Fault Codes and PLC Error Causes and Solutions

PLC Fault Codes

The PLC minor fault codes,

TypeCodeCauseRecovery Method
115·   A 1769 power supply is connected directly to the controller’s 1768 CompactBus, with an invalid configuration.

·   The 1768 power supply powering the controller has failed.

·   Remove the power supply from the 1768 CompactBus and cycle power to the system.

·   Replace the power supply.

31Bus off condition. The connections between the controller and the I/O modules are broken.Complete these steps to identify the source of the BUS OFF fault:

1.    The number of local expansion modules in the project matches the number of modules that are physically installed in the system.


2.    All mounting bases are locked and I/O modules are securely installed on mounting bases.


3.    All 1734 POINT I/O modules are configured to use the Autobaud rate.


If these steps do not remedy the fault condition, contact Rockwell Automation support.

394The current RPI update of an I/O module overlaps with its previous RPI update.Set the RPI rate of the I/O modules to a higher numerical value. Rockwell Automation recommends that the CompactLogix 5370 L2 and

CompactLogix 5370 L3 control systems do not run with Module RPI Overlap


3100The potential exists for data integrity loss with the module because either or both of the input/output size > 16 bytes and the module does not support start and end integrity.Recover methods:

·   Decrease input/output sizes to <= 16 bytes which avoids data integrity loss concern.

·   Contact the module provider to inquire about a version that supports the start and end integrity function.

44An arithmetic overflow occurred in an instruction.Fix program by examining arithmetic operations (order) or adjusting values.
45In a GSV/SSV instruction, the specified instance was not found.Check the instance name.
46In a GSV/SSV instruction, either:

·   Specified Class name is not supported

·   Specified Attribute name is not valid

Check the Class name and Attribute name.
47The GSV/SSV destination tag was too small to hold all of the data.Fix the destination or source so it has enough space.
430Bad parameters passed through to the ASCII port.Verify the ASCII configuration settings.
435PID delta time       0.Adjust the PID delta time so that it is > 0.
436PID setpoint out of range.Adjust the setpoint so that it is in range.
451The LEN value of the string tag is greater than the DATA size of the string tag.·   Check that no instruction is writing to the LEN member of the string tag.

·   In the LEN value, enter the number of characters that the string contains.

452The output string is larger than the destination.Create a new string data type that is large enough for the output string. Use the new string data type as the data type for the destination.
453The output number is beyond the limits of the destination data type.Either:

·   Reduce the size of the ASCII value.

·   Use a larger data type for the destination.

456The Start or Quantity value is invalid.·   Check that the Start value is between 1 and the DATA size of the Source.

·   Check that the Start value plus the Quantity value is less than or equal to the DATA size of the Source.

457The AHL instruction failed to execute because the serial port is set to no handshaking.Either:

·   Change the Control Line setting of the serial port.

·   Delete the AHL instruction.

62Periodic task overlap.

Periodic task has not completed before it is time to execute again.

Make changes such as simplifying programs, lengthening the period, or raising the relative priority.
63Event task overlap.

Event task has not completed before it is time to execute again.

Make changes such as simplifying programs, lengthening the period, raising the relative priority, or slowing the triggering event.
749When the controller loads a project from nonvolatile memory, it logs this minor fault and sets the FaultLog object, MinorFaultBits attribute, bit 7.Clear the fault.
90Unknown error while servicing serial portContact Rockwell Automation Technical Support if the problem persists.
91The CTS line is not correct for current configuration.Disconnect and reconnect the serial port cable to the controller. Verify cabling is correct.
92Poll list error.

A fault was detected with the DF1 master’s poll list, such as specifying more stations than the size of the file, specifying more than 255 stations, trying to index past the end of the list, or polling the broadcast address (STN #255).

Check for the following errors:

·   Total number of stations is greater than the space in the poll list tag.

·   Total number of stations is greater than 255.

·   Current station pointer is greater than the end of the poll list tag.

·   A station number greater than 254 was encountered.

93The RS-232 DF1 Master Active Station Tag is unspecified.Specify a tag to be used for the Active Station Tag on the Serial Port Protocol tab, under Controller Properties.
95DF1 slave poll timeout.

The poll watchdog timed out for slave. The master has not polled this controller in the specified amount of time.

Determine and correct delay for polling.
99The modem contact is lost.

The DCD or DSR control lines are not being received in the proper sequence and/or state.

Correct modem connection to the controller.
910Data has been dropped or lost from the serial port.Slow down the rate at which the initiator is sending data.
1010Battery not detected or needs to be replaced.Install new battery.
1011Safety partner battery not detected or needs to be replaced.Install new battery.
1012The Energy Storage Module (ESM) is not installed.

If the controller is powered-down, the WallClockTime attribute and program are not maintained.

Install an ESM in the controller.
1013The installed ESM is not compatible with the controller.Replace the installed ESM with one that is compatible with the controller.
1014The ESM needs to be replaced due to a hardware fault.

It is not capable of maintaining the WallClockTime attribute or controller program at power down.

Replace the ESM.
1015The ESM cannot store enough energy in the ESM to maintain the WallClockTime attribute or the controller program at power down.Replace the ESM.
1016The uninterruptable power supply (UPS) is missing or not ready.Either:

·   Install the UPS.

·   Check the UPS to make sure it is adequately charged to provide backup power in the event of power loss.

1017The UPS battery has failed and needs to be replaced.Replace the battery in the UPS.
1321Wall Clock Time out of range.Make sure the Wall Clock Time is set to the correct date/time.
1412The Safety project is configured as SIL2/PLd and a Safety Partner is present.Make sure there is no Safety Partner installed to the right of the primary controller.
171…nAn internal controller diagnostic has failed.Contact Rockwell Automation Technical Support with the fault type and fault code.
1735Controller internal temperature is approaching operating limit.Measures should be taken to reduce the ambient temperature of the module. Follow the recommended limits for the ambient (inlet) temperature and apply the required clearance around the chassis.
1736A fan is not present, or is not maintaining desired speed.Replace the fan.
194Ethernet Port FaultEtherNet/IP data storm detected.

Investigate network traffic on the Ethernet port and clear the fault. If problems persists, contact Rockwell Automation Technical Support for further assistance.

201A required license is missing or expired while the controller is in run or test mode.Insert a CmCard containing all licenses required by the project in the controller.