The communication among control modules and scan tool is performed through the Controller area network (CAN) high speed serial data circuit.
The data link connector (DLC) is a standardized 16-cavity connector. The connector provides the following:
| • | Scan tool power battery positive voltage at terminal 16 |
| • | Scan tool power ground at terminals 4 and 5 |
| • | CAN HI communication circuit at terminal 6 |
| • | CAN LO communication circuit at terminal 14 |
The serial data is transmitted on two twisted wires. The twisted pair is terminated with a 120 ohms resistor. The resistor is located in the engine control module (ECM). The resistor is used to reduce noise on the High Speed CAN bus during normal vehicle operation. The high speed CAN is a differential bus. The high speed CAN serial data bus (+) and high speed CAN serial data (-) are driven to opposite extremes from a rest or idle level. The idle level, which is approximately 2.5 volts, is considered recessive transmitted data and is interpreted as a logic 1. Driving the lines to their extremes, adds one volt to the high speed CAN serial data bus (+) and subtracts one volt from the high speed CAN serial data bus (-) wire. This state is interpreted as a logic 0.
