The diagnostic tools to be used will vary depending on the component that needs to be tested as well as the generation your server belongs to.
Here is an article on How to identify which generation your Dell PowerEdge server belongs to.
We recommend that you download a copy of the System Event Logs from your server (using OpenManage Server Administrator or the iDRAC).
Then you should clear the ESM or SEL (System event logs) to remove any old error message and get new error messages which will make the diagnostic easier.
Here are the instructions on How to clear the ESM log on a Dell PowerEdge server.
A specific tool must be downloaded: Dell 32-Bit Diagnostics.
The diagnostic tool is embedded in the Server for ease of use.
You should take a screenshot of any error message that comes up to review when the diagnostics are completed.
For more technical content, you can refer to our online Enterprise Knowledge base.