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WSG-1068 ENGINE CONTROLS
Open Loop and Closed Loop Operation
NOTE: No DTC will be set unless engine has operated
in closed loop status for more than 6 seconds.
The GCP will operate in the following two modes:
Open loop
Closed loop
When the engine is first started, the system is in “open
loop” operation. In open loop, the GCP ignores the
signal from the Heated Oxygen Sensor (HO2S). It uses
a pre-programmed routine to calculate the air/fuel ratio
based on inputs from the TP, ECT, TMAP & CKP
sensors.
The system remains in open loop until the following
conditions are met:
The ECT has reached 95°F (35°C).
15 seconds has elapsed since starting the engine.
After these conditions are met, the engine is said to be
operating in “closed loop”. In closed loop, the GCP
continuously adjusts the air/fuel ratio by responding to
signals from the HO2S (except at wide-open throttle).
When the HO2S reports a lean condition (low sensor
signal voltage), the GCP responds by increasing the
“on” time of the fuel injectors, thus enriching the mixture.
When the HO2S reports a rich condition (high sensor
signal voltage), the GCP responds by reducing the “on”
time of the fuel injectors, thus leaning out the mixture.
Adaptive Learn
Adaptive Learn is a fuel correction coefficient that is
derived from the closed loop correction and is stored in
the GCP’s memory.
The normal purpose of the Adaptive Learn is to
compensate fuel flow for the following:
Fuel composition variance
Engine wear
Component variation
Component degradation
The GCP system will operate in closed loop plus
adaptive learn when the ECT reaches 165°F.
NOTE: The adaptive learn coefficient will get erased if
battery power falls below 9.5 volts.
GCP Service Precautions
The GCP is designed to withstand normal current draws
associated with engine operation. When servicing the
GCP, observe the following guidelines:
Do not overload any circuit.
When testing for opens and shorts, do not ground
or apply voltage to any of the GCP’s circuits unless
instructed to do so.
When measuring voltages, use only a digital
voltmeter with an input impedance of at least 10
megohms.
Do not employ any non-standard practices such as
charging the battery with an arc welder.
Take proper precautions to avoid static damage to
the GCP. Refer to “electrostatic Discharge
Damage” for more information.
Use of Circuit Testing Tools
Do not use a test light to diagnose the engine electrical
systems unless specifically instructed by the diagnostic
procedures. A test light can put an excessive load on a
GCP circuit and result in component damage. For
voltage measurements, use only a digital voltmeter with
an input impedance of at least 10 megohms.
Electrostatic Discharge Damage
Electronic components used in the GCP are often
designed to carry very low voltage. Electronic
components are susceptible to damage caused by
electrostatic discharge. Less than 100 volts of static
electricity can cause damage to some electronic
components. By comparison, it takes as much as 4000
volts for a person to feel the spark of a static discharge.
There are several ways for a person to become
statically charged. The most common methods of
charging are by friction and induction.
An example of charging by friction is a person sliding
across a seat.
Charge by induction occurs when a person with well
insulated shoes stands near a highly charged object
and momentarily touches ground. Charges of the same
polarity are drained off, leaving the person highly
charged with the opposite polarity. Static charges can
cause damage, therefore it is important to use care
when handling and testing electronic components.
CAUTION: To prevent possible electrostatic discharge damage,
follow these guidelines:
Do not touch the GCP connector pins or
soldered components on the GCP board.
Do not open the replacement part package until
the part is ready to be installed.
Before removing the part from the package,
ground the package to a known good ground on
the equipment.
If the part has been handled while sliding across
a seat, while sitting down from a standing
position, or while walking a distance, touch a
known good ground before installing the part
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