Understand the more common or obvious causes of faults, how to test for them and how to rectify them.
The most obvious causes are human error and operational damage. In other words, if things are left alone, then it is more likely that they will continue to work (usually). Even things as simple as a cleaner has unplugged a device can go unnoticed in certain situations. It is always useful to ask the customer involved, what happened just before the fault was noticed.
The knowledge named 'Eliminating the obvious' is considered to be rather important.
In addition, the knowledge is thought to be mostly easy to replace, it is generally learned by study, and there are 2 people available to deliver this knowledge.
Opinion is that it it requires 3 people to deliver this knowledge, it is largely generally used knowledge, and is quite stable knowledge.
The learn time for this node is about 2 weeks. This is based on a typical knowledge entry level to this knowledge area.