For 1990-2009 cars

Regulations require that all automobile manufacturers establish a common communications system. The communication between the powertrain control module and the off-board diagnostic equipment (scan tool) is achieved on a serial communication line. Serial data is sent in linear form, one bit at a time, over the communication line.

### ISO (9141-2) Serial Data

The Chevrolet Metro utilizes the International Organization for Standardization (ISO [9141-2]) communications system. ISO (9141-2) specifies the requirements for setting up the interchange of digital information between the on-board emission-related engine control modules of road vehicles and the OBD II scan tool as specified in J1978. This communication is established to facilitate compliance with California Code of Regulation. The most significant result of this regulation is that the regulation provides the scan tool manufacturers with the capability of accessing data from any make or model vehicle.