Reliability Insights

The 5 WHYS: A quick and easy tool for Root Cause Analysis

As maintenance practitioners, we’ve all have heard about the 5 WHYS.

And chances are, many of you have used this approach to execute root cause analysis at some point in your career.

While it may seem like a simple and easy-to-use tool, you need to approach the 5 WHYS with a deeper understanding of the process and the desired outcome.

In this article, let’s explore what the 5 WHYs is, the misconceptions surrounding the 5 WHYS, and discuss how to effectively utilize it in your organization.

What is the 5 WHYS approach?

The 5 WHYS (sometimes called 5Y) is a simple process developed in Toyota to get to the root cause of a problem by simply asking ‘why‘ five times.

The creator of the Toyota Production System, Taiichi Ohno, described the 5 WHYS as—

“The basis of Toyota’s scientific approach… by repeating ‘WHY’ five times, the nature of the problem as well as its solution becomes clear.”

Many professionals view the 5 WHYS process as an easy and convenient tool for frontline staff to identify the root cause of a failure.

Here’s an example:

A pump failed. Why?
Because a bolt came loose. Why?
Because of a mechanical error. Why?
Because the technician was tired. Why?
Because he/she didn’t get enough sleep.

With the 5 WHYs, you don’t use a complicated process or software like when you do an Apollo RCA. And you don’t need the 2–3-day training to learn the Apollo RCA process either.

The 5 WHYs process doesn’t require statistical analysis or advanced tools. It quickly gets to the heart of the problem. Anyone can use it. And it encourages a structured approach to problem-solving, which can be beneficial in various contexts.

Not only that, but it also encourages team collaboration by allowing you to discuss and question together. Teams can converge on the root cause and collaborate on solutions.

5 WHYs are quick and easy.

They are just what we need! Right?

But are they really?

Despite its apparent simplicity, the 5 WHYS may not be as straightforward as it seems. To make the most of this technique, you must be aware of its limitations and avoid oversimplifying the problem-solving process.

The Problem with the 5 WHYS

The main problem I see with 5 WHYs is that people focus on the tool, instead of focusing on the process and the desired outcome.

People somehow assume that just because the impact of a failure was low, the root causes can be established easily.

Also, some complex problems may have multiple root causes. And the 5 Whys might make it seem like there’s only one. And so there’s a danger of stopping at symptom-level causes without getting to the true root.

And that’s where we go wrong.

We must understand that getting to the bottom of a major failure can be simple. And at the same time, analysing a minor failure could actually turn out to be technically complex.

To avoid this pitfall, you need to approach the 5 WHYS with flexibility and openness to other techniques if the initial analysis indicates a more complex issue.

Using the 5 WHYS Effectively

To maximize the potential of the 5 WHYS, you can use it for what appears to be ‘simple’ failures on the surface. But, be prepared to adopt a more rigorous technique.

If your initial WHY shows that there is a lot more to the story than you initially thought, don’t hesitate to adopt a more comprehensive approach to root cause analysis, such as Failure Modes and Effects Analysis (FMEA) or Fault Tree Analysis (FTA).

And always, always have a proficient reliability engineer review all your 5 whys to ensure quality. Even better, have him or her attend as many 5 WHY sessions as possible to provide valuable input and guidance.

Final Thoughts

The 5 WHYs approach, while simple, is a powerful tool for getting to the heart of a problem. The problem is, using this approach makes your prone to underestimating or overestimating your problems. That’s why, like any tool, it’s essential to be aware of its limitations and use it properly. By combining the 5 WHYs with other problem-solving techniques, you can create a comprehensive approach to tackling your problems head-on.


How are you using the 5 WHYs in your organisation?

Let us know in the comments.

Related Articles

Reliability Insights

The Waddington Effect

Is doing more maintenance ‘good’?   It’s common to think so. I mean, it makes sense that the more maintenance you do… the less likely your

Learn More