GENERAL DESCRIPTION
) ISO 9141 is an international standard for communications between automobiles and diagnostic testers. It specifies a serial data communication bus between the vehicle’s Electronic Control Units (ECUs) and the diagnostic test SAE OBDII Scan Tool (SAE J 1978). ISO 9141 has been adopted by the California Air Resources Board for all cars sold in California with feedback fuel control systems. Similar rules are being adopted in New York, New Jersey, Massachusetts, and Maryland, and are expected to affect the design of most cars sold in the United States. Diagnostic Tester According to SAE J1978 For the same reason, the Fault Detection signal is not bonded out. The fault detection and protection circuitry are active, and the device will shut down in the event of a fault. VDD VB ECU 1 ECU 2 Arrows indicate direction of data flow. RX FIGURE 1. Possible System Configuration VDD – + VB 2 K CS Figure 1 is a system configuration for the ISO 9141 specification. The primary form of communication is with the single-ended K-Line.
Vishay
