Theory Of Operation
Depending upon the vehicle configuration for CAN-C or IHS, there can be multiple Controller Area Network (CAN) Bus Star Connectors located throughout the vehicle. The Star Connectors contain the CAN terminating resistors and are located so that they can be accessed for diagnosis of the CAN Bus networks. For an in-depth explanation of the Controller Area Network (CAN) Bus system operation, refer to DESCRIPTION AND OPERATION .
The (special tool #2073400080, Kit, PowerNet / CUSW CAN BUS Diagnostic Tool), is used in place of a Star Connector to assist in CAN Bus network diagnosis. The diagram on the front displays how the tool is to be used, while the back displays a schematic which will be helpful when using the CAN Bus diagnostic tools. The tool kit consists of a 2-Pin ECU testers and one 3-Pin Star Connector tester.
Wording on the PowerNet / CUSW CAN BUS Diagnostic Tool shows "STAR BLOCK" instead of "STAR CONNECTOR".
2-PIN CAN BUS DIAGNOSTIC TOOL
- The 2-Pin CAN Bus diagnostic tool being used for testing between a Star Connector and Electronic Control Unit (ECU), does not contain an in-line resistor. The CAN Bus Diagnostic Tools use toggle switches to Connect and Disconnect the tool to the CAN Bus network being tested on. When the 2-Pin CAN Bus diagnostic tool is connected to a CAN, it is wired in series to the CAN Bus network. The 2-Pin CAN Bus diagnostic tool uses the flow of the CAN through a Star Connector, through the CAN Bus diagnostic tool , and then downstream to the ECU in question for testing.
CAN Bus systems using Star Connectors are configured with one or two Star Connectors. Those systems having one Star Connector contain a 60.0 Ohm resistor; and systems with two Star Connectors contain 120.0 Ohm terminating resistors that are wired in parallel to allow communication with 60.0 Ohms.
Further testing with the (special tool #2073400080, Kit, PowerNet / CUSW CAN BUS Diagnostic Tool) testing ports are equivalent to the CAN C and IHS Bus (+) and (-) circuits and can be used to read CAN Bus measurements with a DVOM or analyze waveform patterns with an Oscilloscope.
Wording on the PowerNet / CUSW CAN BUS Diagnostic Tool shows "STAR BLOCK" instead of "STAR CONNECTOR".
3-PIN CAN BUS DIAGNOSTIC TOOL
- The 3-Pin CAN Bus diagnostic tool being used for the testing of a Star Connector does contain a separate in-line 120.0 Ohm resistor for each switch. The CAN Bus Diagnostic Tools use toggle switches to Connect and Disconnect the tool to the CAN Bus network being tested on. When the 3-Pin CAN Bus diagnostic tool is connected to a CAN, it is wired in series to the CAN Bus network. The 3-Pin CAN Bus diagnostic tool uses the flow of the CAN through the CAN Bus diagnostic tool , to the Star connector in question for testing, and then continues on to the downstream ECUs.
The 3-Pin resistance table below shows the resistance values the 3-Pin CAN Bus diagnostic tool will add to the CAN being tested.
| SWITCH - TO STAR BLOCK | SWITCH - HARNESS TO OTHER STAR BLOCK | APPROXIMATE RESISTANCE WHEN MEASURED WITH DVOM |
|---|---|---|
| CONNECTED | CONNECTED | OL (OUT OF LIMIT) / PASS THROUGH FOR VEHICLE CAN |
| CONNECTED | DISCONNECTED | 120 |
| DISCONNECTED | CONNECTED | 120 |
| DISCONNECTED | DISCONNECTED | 60 (BOTH SWITCHES IN PARALLEL) |
CAN Bus systems using Star Connectors are configured with one or two Star Connectors. Those systems having one Star Connector contain a 60.0 Ohm resistor; and systems with two Star Connectors contain 120.0 Ohm terminating resistors that are wired in parallel to allow communication with 60.0 Ohms.
Further testing with an oscilloscope or DVOM can be performed at the testing ports of the (special tool #2073400080, Kit, PowerNet / CUSW CAN BUS Diagnostic Tool).