Troubleshooting field aid

Troubleshooting Readiness Gate Checklist

A structured working check for the conditions, controls and evidence needed before diagnostic intervention, during testing and at close-out or transfer.

How to use the gates

Review the gates in order with the person who controls the work and the people competent in the affected systems. Tick an item only when it is confirmed, or when its non-applicability has been assessed and recorded under the project’s requirements.

PassThe applicable checks are satisfied and the authorised reviewer agrees that the work may move to the next gate.

HoldA correctable readiness gap or uncertainty remains. Pause at that gate, resolve or formally control the gap, then review it again.

StopControl has been lost or continued work could increase risk. Cease the activity and place or retain the system in the agreed safe state.

EscalateThe decision, risk or technical issue exceeds the available authority or competence. Transfer it with the evidence preserved.

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Investigation details

Asset or system Location Fault or work reference Date and time Investigation lead Permit or isolation reference

Before diagnostic intervention

Gate 0 Problem definition and intent

Objective: Confirm the reported condition, expected behaviour and purpose of the investigation.

Gate 0 readiness checks

The affected function and reported symptom are described factually, without assuming a cause.
The condition has been observed or independently verified, or the remaining uncertainty is recorded.
The operating state, sequence position, timing and loading at the event are understood.
Relevant alarms, trips, indications, logs and witness observations have been identified and preserved.
Recent maintenance, configuration, operating or environmental changes are known, or explicitly recorded as unknown.
The expected behaviour and the decision the investigation must support are agreed.

Gate 0 decision

Pass — The gate is satisfied; continue within the agreed authority and controls.Hold — A relevant item is open or uncertain; pause, address it and review the gate again.

Hold if the symptom, expected behaviour or investigation purpose remains unclear.

Evidence, action or record reference

Before diagnostic intervention

Gate 1 Tooling and information readiness

Objective: Ensure observations can be obtained safely and with suitable confidence.

Gate 1 readiness checks

The measurements and observations needed to test the initial hypotheses have been identified.
Suitable electrical, mechanical, process, condition-monitoring or inspection tools are available as applicable.
Tools are within their safe working range, suitable for the environment and acceptable under site rules.
Calibration, functional-check and inspection status meet the applicable quality requirements.
Authorised access to current drawings, manuals, logs, trends and diagnostic information is available.
Required test accessories, protective equipment and competent operators are available.

Gate 1 decision

Pass — The gate is satisfied; continue within the agreed authority and controls.Hold — A relevant item is open or uncertain; pause, address it and review the gate again.

Hold if a required measurement cannot be made safely, reliably or by an authorised competent person.

Evidence, action or record reference

Before diagnostic intervention

Gate 2 System limits and boundaries

Objective: Define the investigation boundary, operating envelope and recoverable safe state.

Gate 2 readiness checks

The affected function, equipment boundary and interfaces with connected systems are defined.
Relevant electrical, mechanical, hydraulic, pneumatic, thermal, process and stored-energy domains are identified.
Normal, start-up, transient and test limits are taken from current approved information.
Supply, return, flow direction, medium condition and open or closed path behaviour are understood where relevant.
Temporary, auxiliary, bypassed or non-standard paths and configurations are identified.
The required initial state, interim safe state and restoration method are agreed.

Gate 2 decision

Pass — The gate is satisfied; continue within the agreed authority and controls.Hold — A relevant item is open or uncertain; pause, address it and review the gate again.

Hold if the boundary, applicable limit or method of returning the system to a safe known state is uncertain.

Evidence, action or record reference

Before diagnostic intervention

Gate 3 Dependencies and interactions

Objective: Check that an upstream, supporting or shared service is not being mistaken for equipment failure.

Gate 3 readiness checks

Energy supplies, control enables and command sources required for the function are identified.
Supporting utilities and services are available at the required condition.
Upstream supply and downstream or return paths have been considered.
Shared resources, standby arrangements and cross-system interactions are understood.
Temporary supplies, construction states and other non-standard arrangements are recorded.
Monitoring, communications, permissive and protection dependencies are included in the boundary.

Gate 3 decision

Pass — The gate is satisfied; continue within the agreed authority and controls.Hold — A relevant item is open or uncertain; pause, address it and review the gate again.

Hold if a dependency or connected-system condition could invalidate the proposed test or its interpretation.

Evidence, action or record reference

Before diagnostic intervention

Gate 4 Preconditions, permissives and interlocks

Objective: Establish whether the system has failed or is being correctly prevented from operating.

Gate 4 readiness checks

The blocking condition is identified as a trip, permissive, inhibit, mode, sequence or other controlled state.
The required operating mode, preconditions, sequence position and timing are confirmed.
Interlock and permissive sources are understood from current approved information.
Protective operation is understood before any authorised reset or further test is considered.
Temporary inhibits, overrides, bypasses and maintenance states have been checked and are controlled.
The intended test has defined acceptance criteria, monitoring, authority and restoration requirements.

Gate 4 decision

Pass — The gate is satisfied; continue within the agreed authority and controls.Hold — A relevant item is open or uncertain; pause, address it and review the gate again.

Hold if the reason for an inhibit or protective action is not understood, or if the proposed action could mask it.

Evidence, action or record reference

Before diagnostic intervention

Gate 5 Environmental and site conditions

Objective: Identify external conditions that could affect the equipment, the measurement or safe access.

Gate 5 readiness checks

Temperature, humidity, moisture, condensation and ventilation effects have been considered where relevant.
Contamination, weather, exposure, atmospheric conditions, vibration and movement have been considered.
Equipment and test-instrument environmental limits are not knowingly exceeded.
Environmental constraints on visibility, access, communication and emergency response are understood.
Conditions are compared with the last known good operating state.
Monitoring is in place for any environmental condition that may change during the work.

Gate 5 decision

Pass — The gate is satisfied; continue within the agreed authority and controls.Hold — A relevant item is open or uncertain; pause, address it and review the gate again.

Hold if environmental influence is unresolved or conditions prevent safe, representative observation.

Evidence, action or record reference

Before diagnostic intervention

Gate 6 Access and inspection validity

Objective: Confirm that access and observation quality are sufficient for defensible conclusions.

Gate 6 readiness checks

Access is authorised, stable and suitable for the planned inspection or measurement.
Lighting, visibility, communication and working position support reliable observation.
An external condition check covers damage, leakage, overheating, contamination, looseness and abnormal noise or vibration as applicable.
Enclosures, guards, connections, interfaces and evidence of recent or temporary work have been reviewed.
Critical physical positions are independently verified where indication alone may be insufficient.
Any intrusive inspection has a specific need, competent authority, safe method and restoration plan.

Gate 6 decision

Pass — The gate is satisfied; continue within the agreed authority and controls.Hold — A relevant item is open or uncertain; pause, address it and review the gate again.

Hold if access is unsafe, the observation is inconclusive or intrusive work is not properly controlled.

Evidence, action or record reference

Before diagnostic intervention

Gate 7 Safety and risk control

Objective: Confirm that the investigation can proceed without uncontrolled exposure or defeated safeguards.

Gate 7 readiness checks

All relevant hazards, energy sources and stored or latent energy are included in the task risk assessment.
Permits, isolations and other controls are applied under the site’s approved system of work.
Isolation effectiveness is verified by an approved method before reliance is placed on it.
Protective equipment, barriers, communications and emergency arrangements are suitable and in place.
Any live or energised diagnostic work is specifically justified, authorised and controlled by competent persons.
Stop criteria, changing-condition monitoring and the method for leaving the system safe are understood.
Safeguards removed or disturbed for authorised work have controlled reinstatement and verification requirements.

Gate 7 decision

Pass — The gate is satisfied; continue within the agreed authority and controls.Hold — A relevant item is open or uncertain; pause, address it and review the gate again.

Hold if authority, isolation, safeguards, emergency arrangements or risk controls are incomplete.

Evidence, action or record reference

During the investigation

Gate 8 Structured troubleshooting method

Objective: Keep each test evidence-led, controlled, reversible where practicable and capable of reducing uncertainty.

Gate 8 readiness checks

A short, ranked set of credible hypotheses is based on the verified evidence and system function.
The expected result and decision value of each test are defined before intervention.
Safe, non-intrusive and high-value checks are considered before more disruptive work.
One controlled variable is changed at a time and the original state can be recovered.
Independent and disconfirming evidence is actively sought rather than fitting evidence to a preferred cause.
Actions, readings, settings and results are recorded as the work proceeds.
The method is paused and reviewed when results conflict, risk changes or a test does not reduce uncertainty.

Gate 8 decision

Pass — The gate is satisfied; continue within the agreed authority and controls.Hold — A relevant item is open or uncertain; pause, address it and review the gate again.

Hold and re-plan if method discipline is lost, the evidence becomes unreliable or risk changes.

Evidence, action or record reference

Close-out or transfer

Gate 9 Documentation and handover

Objective: Make the evidence, reasoning, restoration state and remaining limitations traceable.

Gate 9 readiness checks

The original symptom, expected behaviour, operating context and event timeline are recorded.
Evidence sources, measurements, instrument references and relevant test conditions are traceable.
Hypotheses, decisions, actions and rejected causes are recorded with their rationale.
Temporary interventions, changed settings and final configuration are identified and controlled.
Cause, consequence and unresolved uncertainty are clearly distinguished.
Restoration evidence, residual risks, limitations and follow-up actions are recorded.
The receiving authority, owner, next step and approved record location are confirmed.

Gate 9 decision

Pass — The gate is satisfied; continue within the agreed authority and controls.Hold — A relevant item is open or uncertain; pause, address it and review the gate again.

Hold close-out or transfer if another competent person could not understand what was done and why the system state is acceptable.

Evidence, action or record reference

Stop and escalation criteria

Apply the project’s more conservative requirement whenever it sets a lower threshold. The examples below are prompts, not an exhaustive risk assessment.

Stop and make safe when

The safe state, isolation boundary or restoration route is unclear or no longer effective.
An unexpected condition, limit exceedance, loss of containment or protection concern appears.
The proposed test would defeat a safeguard or introduce an uncontrolled temporary condition.
Required authority, competence, tools, access, communication or emergency support is absent.
Personnel, equipment, environment or essential operations could be exposed to unacceptable risk.
Changing conditions, poor evidence quality, fatigue or time pressure make the next action unreliable.

Escalate or transfer when

The issue exceeds the team’s technical competence, work authority or acceptance authority.
A safety-critical, protective, regulated or high-consequence function may be involved.
Evidence conflicts, the fault repeats, or the pattern may affect other systems or assets.
Further work requires design review, specialist testing, configuration or setting changes, or manufacturer input.
The system cannot be returned to a known acceptable state within the approved plan.
Operating restrictions, deferral or continued service require a decision by a higher authority.

Final decision record

Pass / accepted Hold / action required Escalated / transferred Stopped / safe state retained

Decision or limitation reference Next action and owner Reviewed by Date and time

How to use the gates

Stop and escalation criteria

Stop and make safe when

Escalate or transfer when

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