Readout of Fault Code in Automotive

Self-diagnosis System
The fault in vehicle electronic system is stored in KAM of ECU as fault code. The fault code can be read out by the on board diagnostic system or external gm tech2 scan tool.

The on board diagnostic system in different vehicle may indicate the fault in different way. In general, the following ways are popular:
- Blinking of fault indicators on the instrument panel
- Swing of multimeter index
- Blinking of red/green LED on ECU
- Shown by a special device

The more intuitionist way for showing the fault is by external scan tool.

The diagnostic system of modern cars is equipped with diagnostic socket or DLC (data link connector). Fault code in vehicle ECU can be read out by connecting a scan tool to the diagnostic socket. In early time, each vehicle system had its own type of diagnostic socket. Since 1996, SAE has specified a uniform system called OBDII on board diagnostic system. Each vehicle that is made in accordance with the system may have the same diagnostic socket, same definition of pin and same description of fault code. The control units of every system are connected to bus, so only one diagnostic socket is needed for readout of fault code. obd provides the possibility of reading data stream and displaying working status of switches and actuators. Moreover, external scan tool can send commands to activate the actuators.

X431 Master is such an external scan tool for vehicle diagnosis. It not only has the diagnostic function like reading fault code, reading data stream, actuation test, displaying sensor waveform, coding control unit, etc., but also has PDA function.