LONG BLOCK M 20R5379 - Caterpillar

Diagnostic Codes
Diagnostic codes alert the operator that a problem in the electronic system has been detected. Diagnostic codes are also used by the service technician to identify the nature of the problem. Cat® Electronic Technician (ET) is a software program that runs on a personal computer. The software can be used by the service technician to view the diagnostic code information for an ECM. The diagnostic code will be displayed as a two-element code. The following terms describe the elements of the code:Suspect Parameter Number (SPN) - The SPN is a code which is assigned to each component to identify data.Failure Mode Identifier (FMI) - The FMI indicates the type of failure.Refer to Table 1 for a complete list of the diagnostic codes and the appropriate troubleshooting procedure.Note: Do not confuse diagnostic codes with event codes. Event codes alert the operator that an abnormal operating condition such as low oil pressure or high coolant temperature has been detected. If an event code is active, refer to Troubleshooting, "Event Codes".Illustration 1 is an example of the operating range of a sensor.
Illustration 1 g01365757
Example of the typical operating range of a sensor
(1) This area represents the normal operating range of the engine parameter.
(2) In these areas, the engine is operating in an unsafe operating range of the monitored parameter. An event code will be generated for the monitored parameter. The sensor circuit does not have an electronic problem. Refer to Troubleshooting, "Event Codes" for additional information on event codes.
(3) In these areas, the signal from the sensor is outside of the operating range of the sensor. The sensor circuit has an electronic problem. A diagnostic code will be generated for the sensor circuit.Active Diagnostic Codes
An active diagnostic code represents a problem with the electronic control system. Correct the problem as soon as possible.When the ECM generates an active diagnostic code. The "Active Alarm" indicator ("Control Alarm Status" on Cat ET) is activated to alert the operator. If the condition that generated the code is momentary, the message disappears from the list of active diagnostic codes. The diagnostic code becomes logged.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. Each ECM will record the following information when a code is generated:
The hour of the first occurrence of the code
The hour of the last occurrence of the code
The number of occurrences of the codeThis information is a valuable indicator for troubleshooting intermittent problems.A code is cleared from memory when one of the following conditions occur:
The service technician manually clears the code.
The code does not recur for 100 hours.
A new code is logged and there are already ten codes in memory. In this case, the oldest code is cleared.Some diagnostic codes may be easily triggered. 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