Practical Problem Solving – Proving Cause & Effect

By Pascal Dennis

"Improvement is endless and eternal" – Taiichi Ohno

At Toyota I learned the following problem solving drill:

1. Do I have a problem?
2. Do I know the cause?
3. Have I proven cause & effect?
4. Have I confirmed the countermeasure?

Question 3 is a common failure point. Humans are wired to jump to countermeasures. Testing cause and effect, by contrast, takes time. You have to develop a hypothesis, then run experiments to prove, or disprove it.

Recently, our family had the interesting opportunity to apply the drill.

1. Do we have a Problem?

Yes - an annoying rattle coming from the dashboard of our RX 350 Lexus truck. (Very surprising for a vehicle built by the splendid Toyota team in Cambridge Ontario.)


2. Do we know the cause?

After looking under the hood, driving at different speeds, on different kinds of ground, we were unable to locate the source.

(My teenage daughter Katie drolly suggested the rattling was coming from my head, but let’s put that aside.)

Lexus technicians also checked, but detected no evidence of a rattle in the cabin. But soon after, there it was again!

My wife, always alert, then made an interesting observation. “Hmmm, the truck never rattles when you’re wearing your sun glasses.”

And sure enough, when the truck was with Lexus maintenance, I’d taken my sun glasses with me.

You can imagine our next steps. We ran a number of variations on the following experiments:

• Sun glasses in storage position
• Sun glasses on Pascal’s head

The result?

• Sun glasses in storage position – rattle
• Sun glasses on Pascal’s head – no rattle

Thereby, we were able to turn the problem on and off, the ultimate test of cause and effect.

Countermeasures, for our family at least, are clear. But what’s the countermeasure for Lexus, whose marketing extols the world’s ‘quietest cabin’?

An unanticipated failure mode! So it goes. That’s why we say, improvement is endless and eternal!

I have great faith in Lexus. Vibration absorption in the sun glasses storage area comes to mind.

(As for a rattling head, no comment.)

Best,

Pascal

Pascal Dennis Bio