Studio 5000 — How to Clear a Major Fault and Return to Run Mode: Three Methods Compared

This guide covers Studio 5000 how to clear a major fault and return to run mode using three distinct methods — software, hardware keyswitch, and programmatic SSV — so you can apply the right one regardless of what tools are on hand. The production manager is standing next to you. The controller has been in FAULT for 12 minutes. The Studio 5000 workstation is on the other side of the plant, there is no laptop with you at the panel, and no one has told you that the same fault clears in 8 seconds by moving the keyswitch. This happens on the first plant visit for most automation technicians, and it costs more time than the fault itself. Knowing all three methods to clear a major fault and return to RUN — software, hardware, and programmatic — and which faults respond to which method is the information that eliminates that 12-minute delay permanently.

• Before Clearing: Verify You Have Fixed the Root Cause
• Fault Clearability Table: What Can and Cannot Be Cleared
• Method 1: Software Clear via Studio 5000
• Method 2: Hardware Keyswitch — The Fastest Field Method
• Method 3: Programmatic Clear with SSV Instruction
• Confirming the Controller Returned to RUN
• Technical Validation
• Frequently Asked Questions

Before Clearing: Verify You Have Fixed the Root Cause

Clearing a major fault without addressing its root cause results in immediate re-fault: the controller returns to RUN, executes one scan cycle, and faults again on the exact same condition. In most cases, this is worse than the original fault because it generates additional Fault History entries and may indicate to the controller that the condition is recurring — some safety-configured controllers have policies that require human acknowledgement of a recurring fault before the second clearance is permitted.

Minimum pre-clearance verification: 1. Read the fault Type and Code from Studio 5000 (Controller Properties → Faults) or from the controller faceplate display (FLT Txx:yy) 2. Identify the root cause from the Type+Code table — see Allen-Bradley Controllogix Fault Codes Complete List Studio 5000 3. Confirm the physical or software condition causing the fault has been corrected 4. Only then proceed to fault clearance

Fault Clearability Table: What Can and Cannot Be Cleared

Not all major faults are clearable via any of the three methods. Some faults require physical hardware action before the software or keyswitch method has any effect:

Method 1: Software Clear via Studio 5000

Requirements: Studio 5000 online connection to the faulted controller.

Procedure:

1. Studio 5000 → Online (green connection to controller)
2. Controller Properties (right-click controller in project tree → Properties)
3. Faults tab
4. Read and record the fault Type, Code, Sub-code, Task, Routine, Rung
5. Click [Clear Major Faults] button
6. Confirm: "Are you sure you want to clear all major faults?" → Yes
7. Controller transitions to STOPPED state (not faulted, not running)
8. Controller Properties → General tab → Mode → Select [Run] → OK
   OR: Studio 5000 toolbar → Run Mode button (green triangle)

The software clear is the safest method because it requires deliberate action in the software and provides immediate visual confirmation. The fault record is preserved in the Fault History tab even after clearance.

Method 2: Hardware Keyswitch — The Fastest Field Method

Requirements: physical access to the controller module faceplate; keyswitch present (most ControlLogix 1756 processors and CompactLogix 1769-L3x/L4x/L5x have a physical keyswitch; some 1769-L1x/L2x do not).

Procedure:

1. Locate the 3-position keyswitch on the controller faceplate:
   REM (Remote) — PROG (Program) — RUN
2. Current position is typically REM or PROG while faulted
3. Rotate to PROG position → pause 2 seconds
4. Rotate to RUN position

On most Logix5000 controllers, moving to PROG clears the major fault, and moving to RUN starts execution. The transition takes 1–3 seconds for the controller to execute the startup sequence.

Why this works without a laptop: the keyswitch sends a direct hardware signal to the controller OS, bypassing the Studio 5000 software layer. It does not require any network connection or installed software.

Limitation: the keyswitch method does not display or log the fault information before clearing. If the fault was not previously recorded, the fault type is lost (though it remains in the Fault History accessible via Studio 5000 later). Always read the faceplate display (FLT Txx:yy) and note the Type and Code before moving the keyswitch.

Method 3: Programmatic Clear with SSV Instruction

Requirements: the fault clear SSV instruction must already be in the controller program before the fault occurs — it cannot be added after-the-fact while the controller is faulted (the controller is not executing the program in FAULT state).

Use case: automated restart systems where the controller must be able to clear specific, known-safe fault types without human intervention.

Ladder implementation:

[Detect_MajorFault]  ← Contacts: ControllerFaultHandler.FaultCode = 42 (watchdog only, example)
                     ← AND: SafeConditions.bit = 1 (safety interlock)
    |
    [SSV(FaultLog, ., MajorFaultRecord, #ClearValue)]
    where #ClearValue is a DINT array with all zeros = fault clear command
    |
    [SSV(ProgramControl, Program:MainProgram, .Mode, 6)]
    6 = Run mode command

Important restriction: programmatic fault clearance is appropriate only for Type 3 and Type 4 faults where the root cause is known and can be programmatically verified before clearance. Using SSV to automatically clear all fault types regardless of Type and Code is a safety risk — it would clear Type 1 (hardware fault) conditions that indicate the controller is not safe to run.

For the systematic approach to fault identification before clearance, including the 8-step diagnostic framework, see Plc Diagnostic Troubleshooting Systematic 8-Step Guide Industrial.

Confirming the Controller Returned to RUN

After any clearance method, verify the controller state via three sources:

1. Controller faceplate display: shows RUN when executing normally
2. RUN LED: green and solid (not flashing) — flashing RUN LED indicates the controller is in Remote Run mode via keyswitch and may not be executing all tasks
3. Studio 5000 toolbar: shows green RUN indicator; project tree shows controller without fault icon

If the controller returned to RUN for less than one scan cycle and then faulted again, the root cause was not resolved before clearance. Read the new fault record — if it is the same Type and Code, the fix was insufficient. If it is a different fault, the original fault cleared but revealed a second underlying condition.

Technical Validation

Fault clearance methods and clearability specifications from Rockwell Publication 1756-PM014. SSV instruction fault clearance technique from NFM Consulting Allen-Bradley faultfinding diagnostics. Industrial PLC operational training from NIC.edu PLC certification programs.

Frequently Asked Questions

After clearing the fault with the keyswitch, the controller shows REM RUN on the faceplate but not RUN. Is the controller running the program?

REM RUN means the controller is in Remote Run mode — the program is executing, but the keyswitch is in the REM (Remote) position, not the RUN position. This is normal operation on most installations where the keyswitch remains in REM to allow Studio 5000 to change modes remotely. The program executes identically in REM RUN and RUN mode.

The Clear Major Faults button in Studio 5000 is greyed out. What prevents it from being clickable?

The Clear Major Faults button is inactive when: (1) the controller is not currently faulted (no active major fault to clear), (2) the Studio 5000 connection is in Program mode — the button requires the controller to be in a state where the mode change is permitted, or (3) the user account used to connect to the controller does not have the security permission level required for fault clearance. Check the controller security configuration in Studio 5000 → Controller Properties → Security.

Does clearing a major fault also clear the Fault History?

No. Clearing a major fault removes the active fault from the Faults tab but preserves all entries in the Fault History tab. The Fault History accumulates up to 16 entries and is only cleared by a complete memory reset or a deliberate programmatic clear via the SSV instruction targeting the FaultHistory system object. The Fault History persists through power cycles.