Advanced Automotive Fault Diagnosis
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LÔØI NOÙI ÑAÀU, ledklok
- Điều hướng trang này:
- 3.3.2 The scanner/fault code reader
| 3.3 Scanners/fault code
readers 3.3.1 Serial port communications A special interface of the type that is stipulated by ISO 9141 is required to read data. This stand- ard is designed to work with a single or two wire port allowing many vehicle electronic systems to be connected to a central diagnostic plug. The sequence of events to extract data from the ECU is as listed below: ● test unit transmits a code word; ● ECU responds by transmitting a baud rate recognition word; ● test unit adopts the appropriate setting; ● ECU transmits fault codes. The test unit converts these to suitable output text. 3.3.2 The scanner/fault code reader Serial communication is an area that is continuing to grow. A special interface is required to read data. This standard is designed to work with a single or two wire port, which connects vehicle electronic systems to a diagnostic plug. Many functions are then possible when a scanner is connected. They include the following. ● Identification of ECU and system to ensure that the test data is appropriate to the system currently under investigation. ● Read out of current live values from sensors so that spurious figures can be easily recognised. Information such as engine speed, temperature air flow and so on can be displayed and checked against test data. 30 Advanced automotive fault diagnosis Figure 3.7 Pico Technology two-channel PC automotive oscilloscope ● System function stimulation allows actuators to be tested by moving them and watching for suitable response. ● Programming of system changes. Basic idle CO or changes in basic timing can be programmed into the system. Figure 3.8 shows a scanner from snap-on. TAs scanner allows the technician to perform all the necessary operations, such as fault code reading, via a single common connector. The portable hand-held tool has a large graphics display allow- ing clear instructions and data. Context-sensitive help is available to eliminate the need to refer back to manuals to look up fault code definitions. It has a memory so that data can be reused even after disconnecting power from the tool. This scanner will even connect to a controller area network (CAN) system with a suitable adapter. tải về 7.07 Mb. Chia sẻ với bạn bè của bạn:
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