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Computers and Sensors:
On-board Diagnostics
We’ve seen how computers monitor and report information as well as see how computers can use devices to make adjustments to automotive systems. But what happens when a problem is discovered. How does the computer alert the driver of the existence of a problem as well as let the mechanic know what the source of the problem might be?
In addition to monitoring and making adjustments, your vehicle’s computer is also equipped with fairly sophisticated troubleshooting capabilities. Computer modules routinely checks circuits and electrical components for any unusual values that exceed either the minimum or maximum values. If a value falls outside the normal range, then the driver is alerted that a problem exists by the illumination of a warning light on the instrument panel (dash). In addition, a special trouble code is generated and stored in the computer that the mechanic can access with a special computer called a scan tool. Scan tools are specifically designed to help the mechanic identify the cause of problem by locating the source of the problem or run tests. A special connection called the data port, allows the scan tool to plug into the onboard computer and retrieve trouble codes.
 On Board Diagnostics (OBD)
Early diagnostic systems were fairly limited in their ability to monitor vehicle operations and did not offer any uniformity as to how information was stored or how it could be accessed. These earlier systems are known as the first generation of computer assisted diagnostic systems or OBD I. Under pressure from the Environmental Protection Agency (EPA), auto manufacturers were required to expand the types of vehicle functions monitored and to standardize the recording of trouble codes. As a result, the second generation of standardized On Board Diagnostics was developed.
OBD II
The second generation of On Board Diagnostics is largely focused on vehicle emissions but offers significant improvements over earlier generation of diagnostic tools. Nevertheless, OBD II systems can frequently generate as many as 500 trouble codes or more. But equally important has been the standardization of equipment between manufacturers that allows scan tools to hook up to the computer.
Even though manufacturers have standardized a large number of trouble codes and made them relatively easy to access, manufacturers maintain a large number of proprietary codes that are only accessible through proprietary software. |
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1. Onboard Computers and Sensors
2. Computer Chips And The Driveway Mechanic
3. Active and Passive Sensors
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