966M and 972M Wheel Loaders Power Train, Steering, Braking, Hydraulic, and Machine Systems Caterpillar

Illustration 1	g03775530

The illustration above shows the ECMs on the machine and the data links in which the ECMs communicate. The ECMs are as follows:

• Engine ECM (1)

• Transmission ECM (2)

• Implement ECM (3)

• Product Link ECM (5)

Communication between the ECMs is conducted over the data link circuits. The data link circuits are bidirectional, allowing the ECMs to send and receive information. The ECMs support two types of data links:

• Cat Data Link (CDL): The Cat Data Link is used to send system status information between ECMs and Cat ET.

• SAE J1939 (CAN A and CAN B): The SAE J1939 Data Links are used for high speed system operation and communication between ECM controls and the ECMs of other machine systems.

Note: In the event of a failure of the SAE J1939 Data Links, the Cat Data Link is used as a back-up for operational communication.

Other components on the machine use the data links for communication. The display module (6), cab switches (7), and relay driver module (8) communication with the other ECMs over the CAN A Data Link.

Several of the ECMs have the same part number. Each of these ECMs with the same part number are assigned a location code. This location code tells the ECM what functions will be performed. The location code is enabled by grounding pin 32 on the J1 connector. The location code is determined by the grounding of pins 26, 27, 28, or any combination of those pins on the J1 connector. The ECMs can be flashed with a file that is not correct for the location code.

Example: The Implement ECM flash file can be downloaded to the Transmission ECM. If the flash files do not match the location code, a diagnostic code will be activated. Also, the ECM will not respond correctly to inputs and output for the specific system.

Illustration 2	g03775534

Cab Electrical System:

This diagram of the Cab Electronic Control System shows the input components and output components of the Implement ECM. The Implement ECM (1) receives and sends information to/from the machine ECMs (2) - (5), Information Display (6), or Cat ET over the Cat Data Link (CDL) or Controller Area Network (CAN A or CAN B) Data Links (13).

The Implement ECM monitors the condition of the sensors and switches attached to the ECM through the machine wiring harness. The Implement ECM controls the output components, to respond to the inputs from switches, sensors, and machine ECMS.

Illustration 3	g03796672

Relay Driver Module:

This diagram of the Cab Electronic Control System shows the input components and output components of the Relay Driver Module.

The Relay Drive Module (1) receives and sends information to/from the Implement ECM (2) over the Controller Area Network (CAN A) Data Link (3).

The relay driver module receives input signals from the various sensors and switches on the machine and sends the signals to the Implement ECM via the CAN A Data Link. The Implement ECM processes the inputs and makes decisions based on the ECM software and other inputs. The decision is sent to the Relay Driver Module via the data link. The relay driver performs that function or commands other components to fulfill the command from the Implement ECM.

The relay driver module monitors diagnostic conditions and reports events and faults to the Implement ECM.