SPACER 4847181 - Caterpillar

Active Diagnostic Codes
An active diagnostic code represents a problem with the electronic control system. Correct the problem as soon as possible.When an active diagnostic code is generated, the "Active Alarm" indicator ("Engine Control Alarm Status" on Caterpillar Electronic Technician (ET)) is activated. The indicator is used 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.Refer to Illustration 1 for an example of the operating ranges of a sensor.
Illustration 1 g01785898
Example of the typical operating range of a sensor
(1) This area represents the normal operating range of the engine parameter.
(2) In this area, the engine is operating in an unsafe operating range of the monitored parameter. A diagnostic code will be generated for the monitored parameter. The sensor circuit does not have an electronic problem. Refer to Troubleshooting, "Engine Monitoring Parameters" for additional information on these codes.
(3) In these areas, the output voltage of the sensor is too high or too low. The voltage is outside of the normal range. The electronic problem will generate a diagnostic 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. 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.Logged codes are listed in chronological order. The most recent code is listed first.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.Troubleshooting
Before diagnosing an active code and to provide basic troubleshooting of the engine, perform the following steps to diagnose a malfunction:
Download a "Product Status Report" from the ECM. The report provides a record of the current state of the engine.
Obtain the following information about the complaint:
The engine code and the time of the code
Determine the conditions for the code. The conditions will include the engine rpm and the load.
Determine if there are any systems that were installed by the dealer or by the customer that could cause the code.
Determine whether any additional codes occurred.
Verify that the complaint is not due to normal engine operation. Verify that the complaint is not due to error of the operator.
Narrow the probable cause. Consider the operator information, the conditions of operation, and the history of the engine.
Perform a visual inspection. Inspect the following items:
Fuel supply
Oil level
Oil supply
Wiring
ConnectorsIf an electrical problem is intermittent, check that the connectors in the circuit are in good repair. Refer to Troubleshooting, "Electrical Connectors - Inspect".