An Active diagnostic code represents a problem with the electronic control system. This problem should be corrected as soon as possible. When an active diagnostic code is generated, a display module such as the Electronic Monitoring System (EMS) may produce a warning.
When the ECM generates a diagnostic code the ECM logs the code in permanent memory. The ECM has an internal diagnostic clock. The ECM will record the hour of the first occurrence of the diagnostic code. The ECM will record the hour of the last occurrence of the diagnostic code. The ECM will record the number of occurrences of the code. This information is a valuable indicator for troubleshooting intermittent problems. Some diagnostic codes may log occurrences that did not result in complaints. The most likely cause of an intermittent problem is a faulty connection or damaged wiring. The next likely cause is a component failure. The least likely cause is the failure of the ECM. Diagnostic codes that are logged repeatedly may indicate a problem that needs special investigation.
If the symptoms continue, use the proper procedure for troubleshooting the symptoms that have been experienced by the operator.
Note: Always clear logged diagnostic codes after investigating and correcting the problem which generated the code.
The ECM can log events. Events refer to engine operating conditions such as low oil pressure or high coolant temperature. Logged events do not indicate an electronic system problem.
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The diagram indicates output voltage from the coolant temperature sensor. The Cat ET can be used to turn ON the engine monitoring for a specific sensor. When the monitoring is turned ON, the sensor's value and any diagnostic event code will appear on a EMS or on the Cat ET. When the features are turned OFF, the engine monitoring will be disabled, but the event is logged in the ECM.
Programmable Engine Parameters
You may be able to program the engine to perform the following actions in some applications:
- Engine Warning
- Engine Derate
- Engine Shutdown
The Cat ET can be used to activate these features. When the features are activated, the display will appear on the EMS or on the Cat ET. An event will be logged in the ECM. When the features are not activated the display will not appear on a monitoring module but an event will be logged.