Controls Engineer Interview Questions: Technical, PLC & Automation Questions With Answers

Preparing for a Controls Engineer interview? Whether your background is in PLC programming, industrial automation, electrical controls, instrumentation, robotics, or manufacturing systems, employers will want to know more than which technologies you have used.

Experienced Controls Engineers are often evaluated on how well they troubleshoot problems, improve reliability, communicate with maintenance and production teams, manage automation projects, and keep manufacturing equipment running.

This guide covers common Controls Engineer interview questions, including technical, PLC, automation, troubleshooting, and behavioral questions — along with suggestions for building stronger answers.

1. Tell Me About Your Controls Engineering Experience

This sounds simple, but it is one of the most important questions in the interview.

For an experienced Controls Engineer, avoid simply listing technologies. Give the interviewer a concise picture of the environments in which you have worked and the results you have produced.

Your answer might include:

• Years of controls or automation experience
• Industries you have supported
• Types of manufacturing equipment or processes
• PLC and automation platforms you have used
• Major projects, upgrades, installations, or troubleshooting responsibilities
• Improvements in uptime, productivity, quality, safety, or cost

Strong approach: Connect your technical experience directly to business results.

2. What PLC Platforms Have You Worked With?

PLC experience is often one of the first technical areas an employer will explore.

Be prepared to discuss platforms you have actually programmed, modified, commissioned, or troubleshot. Depending on your background, these might include Allen-Bradley/Rockwell Automation, Siemens, Schneider Electric, Mitsubishi, Omron, Beckhoff, or other systems.

Rather than simply naming brands, explain your level of involvement.

For example:

• Developing or modifying ladder logic
• Structured Text or Function Block programming
• PLC hardware configuration
• I/O troubleshooting
• Machine sequencing
• Safety PLCs
• Motion control
• HMI integration
• Commissioning new equipment

3. How Do You Troubleshoot a Machine or Control-System Failure?

This is an especially important question for experienced Controls Engineers.

The interviewer wants to understand whether you have a disciplined troubleshooting process rather than simply replacing components until something works.

A strong answer might explain how you:

1. Gather information from operators or maintenance personnel.
2. Determine exactly when and how the failure occurs.
3. Review alarms, PLC logic, HMI information, and system history.
4. Check inputs, outputs, sensors, communications, drives, and field devices.
5. Isolate the problem systematically.
6. Correct the immediate failure.
7. Determine the root cause.
8. Prevent the issue from occurring again.

If possible, give a real example in which your troubleshooting reduced downtime or prevented a recurring production problem.

4. Describe a Difficult PLC Problem You Solved

This is where experienced candidates can differentiate themselves.

Select an example that demonstrates both technical ability and problem solving. Explain:

• What the equipment was doing
• Why the problem was difficult to diagnose
• How you isolated the cause
• What changes you made
• How you verified the solution
• What improved afterward

Whenever possible, quantify the result. For example, mention reduced downtime, increased production rate, fewer faults, improved scrap rate, or increased equipment availability.

5. What Is Your Experience With HMI and SCADA Systems?

Employers may want to understand whether your experience goes beyond PLC programming.

Be prepared to discuss systems you have used for:

• Operator interfaces
• Alarm management
• Production monitoring
• Historical trending
• Recipe management
• Data collection
• Remote diagnostics

If you have worked with FactoryTalk, Ignition, Wonderware/AVEVA, WinCC, or similar platforms, explain the type of development or troubleshooting you performed.

6. How Do You Handle Intermittent Automation Problems?

Intermittent failures can be some of the most difficult problems in manufacturing.

A good answer should demonstrate patience, structured investigation, and effective use of data.

You might discuss reviewing:

• PLC fault history
• HMI alarms
• System trends
• Network or communication failures
• Sensor behavior
• Cycle timing
• Environmental conditions
• Operator observations

Experienced engineers should also explain how they avoid making changes that create additional problems while diagnosing the original issue.

7. What Is Your Experience With Industrial Networks?

Modern controls systems frequently depend on industrial communications.

An employer may ask about your experience with technologies such as:

• EtherNet/IP
• PROFINET
• Modbus TCP
• DeviceNet
• Profibus
• ControlNet
• OPC / OPC UA
• Industrial Ethernet

Be prepared to describe how you diagnose communication problems between PLCs, drives, HMIs, robots, remote I/O, and other devices.

8. How Do You Improve Equipment Reliability?

This is particularly important for Controls Engineers working in manufacturing plants.

Employers want engineers who do more than react to breakdowns.

Your answer might include:

• Analyzing recurring faults
• Improving PLC diagnostics
• Adding meaningful HMI alarms
• Developing preventive maintenance strategies
• Creating backups and version controls
• Improving sensor reliability
• Reducing nuisance trips
• Improving documentation
• Training maintenance technicians

9. Tell Me About an Automation Project You Led

Senior and Lead Controls Engineer candidates should expect questions about project ownership.

Consider discussing a project involving:

• New manufacturing equipment
• PLC migration or upgrade
• Robotics
• Machine integration
• Production-line expansion
• SCADA implementation
• Plant automation improvements

Explain your involvement from planning through startup, including vendors, contractors, programming, commissioning, documentation, training, and production support.

10. How Do You Work With Maintenance and Production Teams?

Technical ability alone does not make a successful Controls Engineer.

Employers want engineers who can communicate with operators, technicians, electricians, mechanics, engineering management, production management, and outside vendors.

Give examples showing that you can explain technical issues clearly, listen to the people operating the equipment, and work collaboratively when production is under pressure.

11. What Would You Do If a Critical Machine Went Down at 2:00 AM?

This question evaluates technical judgment as well as your attitude toward plant support.

For manufacturing Controls Engineers, employers often value people who understand the urgency of production downtime.

A strong answer should demonstrate that you would:

• Assess safety first
• Gather accurate information
• Help isolate the failure quickly
• Communicate with plant personnel
• Restore production safely
• Investigate the root cause after the immediate issue is resolved

12. What Programming Languages Do You Use?

Depending on the position, the interviewer may ask about:

• Ladder Logic
• Structured Text
• Function Block Diagram
• Sequential Function Chart
• Python
• SQL
• VBA
• C / C++

Focus primarily on languages you have used in real industrial applications rather than simply listing everything you have encountered.

13. How Do You Document Controls Changes?

Experienced Controls Engineers know that undocumented changes can create major problems later.

You may want to discuss:

• PLC program backups
• Version control
• Electrical drawings
• Change logs
• Network documentation
• HMI documentation
• Standard operating procedures
• Maintenance troubleshooting guides

14. How Do You Approach Controls-System Safety?

Safety should be part of nearly every controls decision.

Depending on your experience, discuss items such as:

• Machine guarding
• Emergency stops
• Safety relays
• Safety PLCs
• Interlocks
• Lockout/tagout considerations
• Risk assessments
• Applicable industry standards

Never suggest bypassing a safety device simply to keep production running.

15. Why Are You Considering a New Controls Engineering Position?

Experienced candidates should prepare carefully for this question.

Good reasons may include:

• Greater technical responsibility
• More challenging automation projects
• Career advancement
• Leadership opportunities
• Working with newer technologies
• Relocation
• Long-term career growth

Keep your answer positive. Avoid criticizing your current or previous employer.

Controls Engineer Interview Tip: Prepare Examples, Not Just Answers

One of the biggest differences between an average interview and an excellent one is specificity.

Instead of saying:

“I’m very good at troubleshooting PLC problems.”

tell the interviewer about a particular failure, how you diagnosed it, what you changed, and what happened afterward.

Employers remember stories and measurable results.

Before your interview, prepare several examples involving:

• A difficult troubleshooting problem
• A major automation project
• An equipment reliability improvement
• A PLC or controls upgrade
• A disagreement or challenge with another department
• A situation involving significant production downtime
• A project where you saved money or improved productivity

Prepare for the Salary Conversation Too

The interview process may eventually lead to a discussion about compensation.

Experienced Controls Engineers should have a realistic understanding of their market value before discussing salary, bonus opportunities, relocation assistance, or other compensation.

Researching compensation beforehand can help you evaluate an offer and negotiate more confidently.

Final Thoughts

A strong Controls Engineer interview is not simply a test of how many PLC platforms or programming languages you know.

Employers are looking for experienced engineers who can solve difficult problems, reduce downtime, improve automation systems, communicate effectively, and help manufacturing operations become safer and more reliable.

Prepare real examples from your career, understand the employer’s manufacturing environment, and be ready to explain not only what you did but what improved because you did it.