Communication on the Internal Network

Communication On The Internal Network

CAN communication
ECM (Engine Control Module) sends out and receives the following signals via the network:

Brake Control Monitoring (BCM)
Provides information so that the Engine Control Module (ECM) can determine whether any misfiring is due to road condition or to a fault in the engine management system. Also provides a vehicle speed signal.

Climate Control Module (CCM)
Informs the Engine Control Module (ECM) about A/C selection and requests A/C activation.

Central Electronic Module (CEM)
Is the "main computer" in the network and coordinates required information between other modules. It also controls diagnostic function by connecting the Diagnostic Connector to the network for programming and reading off diagnostic trouble codes (DTCs) and parameters. The CEM also includes the Immobilizer.

Steering Wheel Module (SWM)
Provides information to the Engine Control Module (ECM) that the cruise control is selected and that the driver requests changing the cruise control speed.

Transmission Control Module (TCM)
The Transmission Control Module (TCM) is only implemented in automatic transmission cars. The following signals are being sent on the network from the Engine Control Module (ECM) and picked up by the Transmission Control Module (TCM):
- Engine load
- Throttle opening
- Response to torque limiting
- Accelerator and brake pedal position
- Cruise control status.

The following signals are sent out on the network from the Transmission Control Module (TCM) and taken up by the Engine Control Module (ECM):
- Request for torque limiting step I and II
- Request to light Malfunction Indicator Lamp (MIL)
- Signal for constant idle speed compensation (P/N position)
- Engaged gear.

Diagnostic Connector
The serial communication via the Diagnostic Connector is used when reading off the Volvo on-board diagnostic (OBD) system.

Serial communication
ECM (Engine Control Module) communicates serially with the Diagnostic Connector.