The code is broken down into a letter and four numbers. The letter indicates the system where the failure was detected. The first digit identifies the code as a generic or manufacturer-specific entity. The second digit indicates the sub system responsible for the code. The final two zero in on the component or component group that has failed. It should be noted that the snapshot data is only retrievable with a scan tool with a more sophisticated and expensive tool. The Equus 3100 code reader comes with a manual that has more than 50 pages of code definitions.

The code reader merely identifies the troublesome system and the course of action beyond initial identification depends on many other factors. But limiting the realm of possibilities is an important first step to curing what ails. If information is power, this unit is an excellent candidate for the savvy enthusiast's toolbox.

LED Screen Breakdown
1.Monitor Icon
2.Run Icon-indicates the status of the device
3.Done Icon-indicates the vehicle test is complete
4.Link Icon-indicates the reader is linked to the ECU
5.Vehicle Icon-indicates that the reader is being powered by the vehicle
6.Computer Icon-used for expanding the system via computer link
7.Reader Battery Icon-indicates the battery status of the battery inside the reader
8.DTC Display Area-where the trouble code appears on the reader
9.Pending Icon-indicates the currently displayed code is a pending code (Type 2)
10.Code Sequence Icon-when there are more than one code this counter indicates which code is presently being displayed.
11.Code Icon-identifies the code number sequence area
12.MIL Icon-indicates the status of the MIL Malfunction Indicator Light (check engine light)
13.Monitor Icons-indicates which monitors are utilized on the vehicle being tested and if the monitor has run its diagnostic tests. A solid icon means the test of that icon has been competed. A flashing icon means the corresponding system has not been tested. Any icons not illuminated means the corresponding monitor is not used on the vehicle being tested.

J.C. Whitney