GEAR 3526115 - Caterpillar

Active Diagnostic Codes
An active diagnostic code represents a problem with the electronic control system. Correct any active diagnostic codes 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.
Illustration 1 g00740986Illustration 1 indicates a typical output voltage from the coolant temperature sensor. Cat ET can be used to monitor the output voltage and temperature of any sensor. Cat ET will display diagnostic codes that are associated with a sensor. As you look at Illustration 1, notice the output voltage of the sensor. A diagnostic code is generated when the ECM detects an abnormal output voltage from the sensor.Note: Always clear logged diagnostic codes after investigating and correcting the problem which generated the code.Logged Diagnostic Codes
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 following information: the hour of the first occurrence of the diagnostic code, the hour of the last occurrence of the diagnostic code and 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.