ISO Keyword Protocol 2000 Serial Data

Regulations require that all automobile manufacturers establish a common communications system. The Catera uses International Organization for Standardization (ISO) Keyword Protocol 2000 serial data. This system utilizes a single wire bi-directional data line between the Engine Control Module (ECM), the transmission (TCM) and the scan tool. With this type of communication, a voltage level of less than 20 percent of B+ on the data line is considered a logic 0. A voltage level that is more than 80 percent of B+ is considered a logic 1. The message structure is a request and response arrangement that has some similarities to the UART system.