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| Illustration 1 | g00728001 |
Block diagram of the brake ECM | |
The 777D trucks are equipped with an electronic control module for controlling both the Automatic Retarder Control (ARC) and the Traction Control System (TCS). Three possible arrangements can be installed on a truck:
- ARC Only
- TCS Only
- ARC And TCS
Each machine configuration uses a separate ECM. Each ECM has an individual part number. Also, each ECM requires a separate FLASH software in order to instruct the ECM about the machine configuration. A separate part number is available for each FLASH software for each ECM.
The brake ECM receives information from the following input components: engine output speed sensor (EOS), retarder pressure switch, right wheel speed sensor, left wheel speed sensor and TCS test switch.
The brake ECM determines whether the service brakes and retarder brakes should engage for the function of the Automatic Retarder Control (ARC). This action is accomplished by sending signals to the various components of the ARC.
The brake ECM determines whether the parking and secondary brakes should engage for the function of the Traction Control System (TCS). This action is accomplished by sending signals to the various components of the TCS.
The brake ECM receives information from the following output components: ARC supply solenoids, control solenoids, retarder ENGAGED lamp, TCS selector solenoids, proportional solenoids and TCS ENGAGED lamp.
The brake ECM also provides the service technician with enhanced diagnostic capabilities. This is available through the use of onboard memory. Onboard memory stores the possible diagnostic codes for retrieval at the time of service. Service personnel should use the Electronic Technician service tool (ET) for troubleshooting.
Some of the diagnostic functions and programming functions that the service tool can perform are:
- Display the real time status of the input and output parameters.
- Display the internal clock hour reading.
- Display the number of occurrences and the hour reading of the first and last occurrence for each logged diagnostic code and event.
- Display the definition for each logged diagnostic code and event.
- Display the supply and control solenoid engagement counter.
- Program the ARC control speed.
- Perform ARC diagnostic tests.