Communication

COMMUNICATION

COMMUNICATION K-LINES
The K-Lines are a group of circuits that connect each control module to the Data Link Connector (DLC). Each control module is connected to the DLC with a single K-Line. The DRBIII(R) uses the K-Line to communicate with each control module. With the use of the K-Lines the DRBIII(R) is able to read each control modules DTCs, sensor displays, I/Os etc. If DRBIII(R) communications with a particular control module is lost, one of the possible causes could be a fault in the modules K-Line.

NOTE: It is important to note the DRBIII(R) uses the K-Lines for diagnostic and monitoring functions and is no way connected to the CAN data bus network.

The following modules that use the K-line on this vehicle are:
- Airbag Control Module (ACM)
- Automatic Temperature Control (ATC)
- Cabin Heater Module (CHM)
- Central Timer Module (CTM)
- Controller Antilock Brake (CAB)
- Engine Control Module (ECM)
- Heater Booster Module (HBM)
- Instrument Cluster (IC)
- Shifter Assembly (SA)
- Security System Module (SSM)
- Sentry Key Remote Entry Module (SKREEM)
- Transmission Control Module (TCM)

CAN BUS
The CAN bus (controller area network) is a data bus system specifically design for inter module communication on this vehicle. The CAN bus consists of a special twisted two-core cable. Control modules are connected to this "twisted pair". The CAN bus incorporates two terminating resistors. One terminator is built into the Engine Control Module (ECM) and the other is built into the Sentry Key Remote Entry Module (SKREEM). Each resistor has a value of 120 ohms. The resistor condition can be confirmed by disconnecting the control module and measuring the resistance value at the appropriate control module pins. This measurement should read 120 ohms. The two CAN circuits, CAN C Bus (+) and CAN C Bus (-), are bridged by these two terminating resistors when all control modules are connected to the bus. These two resistors are connected to the CAN bus network in parallel. The measurement between the two twisted CAN circuits, with both the ECM and SKREEM connected, should measure a value of 60 ohms.

The CAN bus is bi-directional. This means that each connected control module can send and receive information. Transmission of data takes place redundantly via both circuits. The data bus levels are mirrored, meaning that if the binary level on one circuit is 0, the other circuit transmits binary level 1 and vice versa. The two line concept is used for two reasons: for fault identification and as a safety concept.

If a voltage peak occurs on just one circuit, the receivers can identify this as a fault and ignore the voltage peak. If a short circuit or interruption occurs on one of the two CAN circuits, a software-hardware linked safety concept allows switching to a single-line operation. The defective CAN circuit is shut down. A specific data protocol controls how and when the participants can send and receive.

NOTE: It is important to note the CAN Bus circuits are used for inter-module communication only, and is no way connected to the K-Lines.
The following modules that use the CAN Bus on this vehicle are:
- Automatic Temperature Control (ATC)
- Controller Antilock Brake (CAB)
- Engine Control Module (ECM)
- Instrument Cluster (IC)
- Sentry Key Remote Entry Module (SKREEM)
- Shifter Assembly (SA)
- Transmission Control Module (TCM)