Massachusetts Vehicle Check - Mass08 Management Module ...

Non-Commercial
1. A method to inform the driver of the vehicle that there is a problem. This was
accomplished by
installing a light in
or around the
instrument panel that will illuminate the moment the on-board computer detects a
problem or malfunction. This light is commonly known as the Malfunction Indicator
Light (MIL) and normally displays: “Service Engine Soon!,” “Check Engine,” or the
universal engine symbol.
2. A method for the on-board computer to detect and store system failure data. This was
accomplished by developing a coding system. The on-board computer will store a
specific code when a malfunction is detected. These codes are commonly known as
Diagnostic Trouble Codes (DTC). The on-board computer stores DTCs in order of
priority depending on the nature of the malfunction and the system(s) affected.
3. A method to communicate with the on-board computer to
retrieve the stored information. This was accomplished by
developing a standardized protocol that can communicate
with the on-board computer and by providing an access port
to the vehicle’s on-board computer. In the repair industry, this test equipment is
commonly known as a “scanner” or a “scan tool.” The access port in the vehicle is
commonly known as the “Data Link Connector” or “Diagnostic Link Connector”
(DLC). The DLC configuration and placement in the vehicle were also standardized
by OBD II regulations.
The data link connector contains sixteen (16) cavities for various, but specific
functions. Pin 16 for instance, is supplied with a constant battery voltage that allows scan tool
manufacturers to power their tool. Pins 2, 6, 10, and 14 are utilized by different types of
communication protocols for executing dialog between a scan tool and the vehicle’s
computers. Pins 4 and 5 are designated for signal and or sensor grounds. Some cavities have
Massachusetts Vehicle Check
Ch. 1 - 12