CARRIER-PLANETARY 1620270 - Caterpillar

The electronic control module has some self-diagnostic ability. When an electronic problem with an input or an output is detected, a diagnostic code is generated. This indicates the specific problem with the circuitry.Diagnostic codes are also generated when an abnormal engine operating condition is detected. For example, a diagnostic code will be generated if the low oil pressure alarm is activated. In this case, the diagnostic code indicates the symptom of a problem. This type of diagnostic code is called an event. An event is triggered by the detection of an abnormal engine operating condition.A diagnostic code which represents a problem that currently exists is called an active code.A diagnostic code that is stored in memory is called a logged code. Always service active codes prior to servicing logged codes. Logged codes may include the following categories:
Intermittent problems
Recorded events
Performance historyLogged codes may not indicate that a repair is needed. The problems may have been repaired since the logging of the code. Logged codes may be helpful to troubleshoot intermittent problems.