Module Identifier (MID) - The MID is a code with two or three digits that indicates the electronic module which generated the diagnostic code. Some electronic displays do not display the MID because the module which generates the code is obvious. Table 1 is a list of the module identifiers for this application.
| Module Identifiers | |
|---|---|
| MID | Description |
| 30 | Caterpillar Monitoring System |
| 36 | Electronic Control Module (ECM) for the engine |
| 81 | Machine Control Module (WTL) |
| 82 | Transmission Control Module |
| 74 | Payload Control System (only 988G) |
Component Identifier (CID) - The CID is a number with three or four digits. The CID indicates the component that generated the code. For example, the CID number 17 identifies the fuel shutoff valve.
Failure Mode Identifier (FMI) - The FMI is a two digit code that indicates the type of failure. Table 2 is a list of the failure mode identifiers.
| Failure Mode Identifiers | |
|---|---|
| FMI | Description |
| 00 | The data is valid, but the data is above the normal range of operation. |
| 01 | The data is valid, but the data is below the normal range of operation. |
| 02 | The data is erratic, intermittent, or incorrect. |
| 03 | The voltage is above normal or shorted high. |
| 04 | The voltage is below normal or shorted low. |
| 05 | The current is below normal or the circuit is open. |
| 06 | The current is above normal or the circuit is grounded. |
| 07 | The mechanical system is not responding correctly. |
| 08 | There is a frequency, a pulse width, or a period that is abnormal. |
| 09 | There has been an abnormal update. |
| 10 | There has been an abnormal rate of change. |
| 11 | The failure mode is not identifiable. |
| 12 | The device or the component is faulty. |
| 13 | The device or the component is out of calibration. |
| 14-31 | Reserved |
Note: Do not confuse diagnostic codes with event codes. For information on event codes, see Troubleshooting, "Event 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, a warning may be displayed on an electronic display such as the Caterpillar Monitoring System.
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 when a code is generated:
- Hour of the first occurrence of the code
- Hour of the last occurrence of the code
- Number of occurrences of the code
This information is a valuable indicator for troubleshooting intermittent problems. Any logged diagnostic codes will automatically be deleted if no additional occurrences are recorded in 100 hours. 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 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.