RENR5042-02 53 Troubleshooting Section Illustration 10 indicates the signal range for a typical analog sensor. Diagnostic codes will be generated if the sensor’s output signal is below 0.2 VDC or above 4.8 VDC. i02172201 Diagnostic Code Cross Reference Active Diagnostic Codes SMCS Code: 1900 An active diagnostic code represents a problem with the electronic control system. Correct the problem as soon as possible. Problems with the electronic control system are reported via these types of codes: flash codes, SPN/FMI codes, diagnostic codes, and event codes.
When the ECM generates an active diagnostic code, the “Active Alarm” indicator (“Engine Control Alarm Status” on Cat ET) is activated in order 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. For information on flash codes, refer to Troubleshooting, “Flash Codes”. For information on SPN/FMI codes, refer to Troubleshooting, “Diagnostic Codes”. For information on diagnostic codes, refer to Troubleshooting, “Diagnostic Codes”. Logged Diagnostic Codes For information on event codes, refer to Troubleshooting, “Event 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: Use Table 14 as a cross reference between the various types of codes. The hour of the first occurrence of the code The hour of the last occurrence of the code The number of occurrences of the code This 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 failure. The least likely cause is the failure of an electronic module. Diagnostic codes that are logged repeatedly may indicate a problem that needs special investigation. Note: Always clear logged diagnostic codes after investigating and correcting the problem which generated the code.