Actron CP9035 Insrucciones página 17

COMPUTER BASICS
the sensors listed above, and by looking up the appropriate numbers on a data
table. However, it now checks itself to determine whether the fuel mixture is
correct. It is able to check itself by using the information provided by the oxygen
sensor(s) (O2S) in the exhaust manifold. The oxygen sensors will tell the
computer if the engine is running rich or lean, and the computer can take steps
to correct the situation. In this way, the computer closes the adjustment loop by
checking itself and making necessary corrections. It should be noted that the O2
sensors must be at a very high operating temperature (approximately 650° F)
before they will begin to feed information back to the computer. This is why open
loop mode is necessary—to give the O2 sensors time to warm up to operating
temperature.
As long as the engine and O2 and Coolant Temperature Sensors are at operat-
ing temperature, the computer can operate in the closed loop mode. Closed loop
mode insures that the air/fuel mixture is at the ideal 14.7:1 air/fuel ratio needed
for efficient combustion. In stop and go cycles, the O2 sensor may cool down
enough that the computer will need to rely on a set of internal parameters and go
into open loop mode again. In some cases, this may also happen during
extended periods of idling. Many newer vehicles now use heated O2 (HO2S)
sensors to prevent this condition.
In many vehicles, the computer controls other systems related to open and
closed loop modes, including idle speed, electronic spark control, exhaust gas
recalculation, and transmission torque converter clutches. In open loop mode,
some of these systems will be adjusted to speed the warming of the engine and
get the computer into closed loop mode as quickly as possible.
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