Toyota Motor Corporation First Uses RCA
The 5 Whys method developed by Toyoda was first used during the development of Toyota’s manufacturing processes in 1958. Toyota required all new employees to learn about this process as part of their initiation into the Toyota Production System.
The 5 Whys Method
The 5 Whys method is one of the earliest models used in the history of the root cause analysis, and it simply seeks to ask “why" five times until the main cause of the problem is revealed. This technique systematically rules out other causes each time a “why" is asked. For example:
Problem: The computer monitor is not working.
Why? The monitor's light signal is not on.
Why? The monitor's power cord is not functioning.
Why? The cord is damaged.
Why? It was placed under a heavy load.
Why? I didn't place the cords properly when the monitor was plugged in, which caused damage.
The answer to the last why is the root cause of the initial problem of the computer monitor not working.
Although this system was praised by Toyota Production System’s initial architect, it was later criticized by Teruyuki Minoura, the managing director of global purchasing for Toyota. He called the process as too basic; lacking the proper depth and knowledge needed to find the right causes. One of the main problems identified with the method was that it was not standardized. Different employees asked new sets of “whys" each time, based on their own experiences and depth of knowledge. There was also no method of knowing if the questions asked were the correct questions to be asked in the first place. It has been revealed, however, that this issue can be offset by verifying the questions before they are asked.