Onboard Diagnostics
DIAGNOSTIC TROUBLE CODES (DTCs)
Onboard Diagnostics
COMPUTER ENGINE CONTROLS
The Introduction of Electronic Engine Controls
As a result of increased air pollution (smog) in large cities, such as Los
Angeles, the California Air Resources Board (CARB) and the
Environmental Protection Agency (EPA) set new regulations and air
pollution standards to deal with the problem. To further complicate matters,
the energy crisis of the early 1970s caused a sharp increase in fuel prices
over a short period. As a result, vehicle manufacturers were not only
required to comply with the new emissions standards, they also had to make
their vehicles more fuel-efficient. Most vehicles were required to meet a
miles-per-gallon (MPG) standard set by the U.S. Federal Government.
Electronic Computer Control Systems make it possible for
vehicle manufacturers to comply with the tougher emissions and
fuel efficiency standards mandated by State and Federal
Precise fuel delivery and spark timing are needed to reduce vehicle emissions.
Mechanical engine controls in use at the time (such as ignition points,
mechanical spark advance and the carburetor) responded too slowly to driving
conditions to properly control fuel delivery and spark timing. This made it
difficult for vehicle manufacturers to meet the new standards.
A new Engine Control System had to be designed and integrated with the
engine controls to meet the stricter standards. The new system had to:
¾ Respond instantly to supply the proper mixture of air and fuel for any
driving condition (idle, cruising, low-speed driving, high-speed driving,
etc.).
¾ Calculate instantly the best time to “ignite” the air/fuel mixture for maximum
engine efficiency.
¾ Perform both these tasks without affecting vehicle performance or fuel
economy.
Vehicle Computer Control Systems can perform millions of calculations each
second. This makes them an ideal substitute for the slower mechanical engine
controls. By switching from mechanical to electronic engine controls, vehicle
manufacturers are able to control fuel delivery and spark timing more precisely.
Some newer Computer Control Systems also provide control over other
vehicle functions, such as transmission, brakes, charging, body, and
suspension systems.
D900 CanScan 12
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