The Data link is used for ECM, monitoring system, and service tool communication.
The data links are bidirectional. Each ECM can send information and each ECM can receive information.
The two types of data links are listed below.
Cat Data Link - The Cat Data Link is used to send information on the system status. The information is sent between each ECM, the monitoring system, the product link, and AVSpare Electronic Technician (ET). All the diagnostic codes of the monitoring system are activated by using the Cat Data Link.
SAE J1939 Data Link - The SAE J1939 Data Link is a high speed data link. The J1939 Data Link is used for high speed communication between each ECM and the control modules of other machine systems.
In the event of a failure of the SAE J1939 Data Link, the Cat Data Link is used as a backup system for operational communication.
All electronic control modules that use the Cat Data Link have a module identifier (MID). The module identifiers that follow are valid for the machines that are the subject of this service manual module:
Module Identifiers (MID)
- Machine Electronic Control System ... 39
- Engine Electronic Control ... 36
Both of the data links on the machine are monitored by the machine ECM for abnormal conditions. The machine ECM will activate diagnostic codes for a specific control module and the circuit of the data links when an abnormal condition is detected.
When the machine ECM detects an abnormal condition in the circuit of a data link, the ECM will activate a companion diagnostic code. The companion diagnostic code appears with the diagnostic code for the involved control module. The companion diagnostic codes for the monitoring system are listed below:
CID 0247 - FMI 09 or FMI 14 - SAE J1939 Data Link
CID 0248 - FMI 09 or FMI 14 - Cat Data Link
An example of the companion diagnostic codes that are used by machine ECM is shown below:
The machine ECM is communicating with the engine ECM over the J1939 data link. However, some expected data is not being communicated. The machine ECM will activate the CID 0296 FMI 14 diagnostic code for the engine ECM. The machine ECM will also activate the CID 0247 - FMI 14 companion diagnostic code. The companion diagnostic code will indicate the data link that is involved. The companion diagnostic code will be cleared when the primary diagnostic code is cleared.
The following companion diagnostic codes will be activated when any of the following module communication codes are activated by the machine ECM:
CID 1603 - Machine ECM
CID 0588 - Messenger
CID 0590 - Engine ECM