MICROSCAN User Manual - Snap-on

On-Board Diagnostics (OBD) OBD-II/EOBD Limitations
4.1.2 EOBD Start-up Phase
The European vehicle manufacturers also needed time to phase in and develop EOBD tests and
software in their electronic control modules (ECMs). Some of the manufacturers already had
experience with the USA OBD-II. Others may still have to improve their most recent software
versions. This means that EOBD is experiencing similar phase in problems as OBD-II, with some
2001 and 2002 vehicles having limited EOBD functionality.
4.2 OBD-II/EOBD Limitations
Generic OBD-II/EOBD data is currently limited to:
• Emission diagnostics or
• Problems related to the Malfunction Indicator.
Access to all available data in the ECM (other systems, other parameters, enhanced diagnostics)
will still require a scan tool with manufacturer specific capabilities.
4.3 OBD-II/EOBD Advantages
The advantage of OBD-II and EOBD is the simple “Plug and Play” function:
• Unlike using a manufacturer specific scan tool or vehicle communication software, one does
not have to select the vehicle make, year or model.
• The communication protocol can be automatically detected by the scan tool software.
• Depending on the ECM and amount of parameters selected, data update rates may vary. By
using functions as Custom Data List and <strong>Manual</strong> Select PID in Service $01, sometimes data
update rates may be higher than with manufacturer specific software. This can be helpful in
finding intermittent signal gulches.
Data and monitors that are not described in the OBD/EOBD standards are filtered out, although
they are selectable.
4.4 Communication Protocols
A communication protocol is a standardized way of data communication between an ECM and a
scan tool.
For vehicles that comply with OBD-II and EOBD, the following communication protocols are
permitted:
• ISO 9141-2 (K-LINE)
• SAE J1850 PWM (Pulse Width Modulation) and VPW (Variable Pulse Width)
• ISO 14230-2 (Keyword Protocol 2000)
• ISO 15765-4 (CAN)
The scan tool can be setup so it will automatically determine the communication protocol used in
the vehicle under test.
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