Engine distributors WSG-1068, Service Manual, Page: 270 / 331

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WSG-1068 ENGINE CONTROLS
speeds (with customer-specified minimum and
maximum) based on a variable signal input.

It can be an electronic replacement for a throttle
cable with maximum speed governing (throttle-
bywire).

Or it can switch between throttle-by-wire and a
second fixed or variable input based on a
neutral/parking brake signal.
With the GCP system, a laptop and a communications
cable, diagnosis becomes simpler. The technician can
either view engine data with a real time graphing
program, or store that data into a numeric data file.
Every time a fault is set, the laptop will give you detailed
information about the fault, including:

when it happened

if the fault still exists

a list of essential engine data from the time of
the fault.
It can also display a 10 second graph of critical engine
data, from 8 seconds before the fault occurred to two
seconds after. And if you only want to view engine
parameters and fault codes, all you need is a Personal
Digital Assistant (PDA) and our easy to load software
and a communications cable.
With many OEMs using control modules to control their
machinery, the GCP has the ability to communicate
engine data to and receive commands from other
control modules through a Controller Area Network
(CAN) link, with messages written in the J1939 protocol.
This allows large amounts of data to move throughout
the machine through only two wires, and can be used to
run some module based gauge packages.
The GCP also carries auxiliary features that can be
programmed to control OEM devices, allowing the OEM
to eliminate components from their machinery.
The GCP is also equipped with multiple safety and
protection devices that protect the user and engine from
hazards such as:

over speed

over temperature

over voltage

low oil pressure

unauthorized tampering

over cranking starter motor.
The GCP controls the following:

Fuel metering system

Ignition timing

On-board diagnostics for engine functions
The GCP constantly observes the information from
various sensors. The GCP controls the systems that
affect engine performance. The GCP performs the
diagnostic function of the system. It can recognize
operational problems, alert the operator through the
Malfunction Indicator Lamp (MIL), and store diagnostic
trouble codes (DTC’s). DTC’s identify the problem
areas to aid the technician in making repairs.
The GCP supplies either 5 or 12 volts to power various
sensors or switches. The power is supplied through
resistances in the GCP which are so high in value that
a test light will not light when connected to the circuit. In
some cases, even an ordinary shop voltmeter will not
give an accurate reading because its resistance is too
low. Therefore, a digital voltmeter with at least 10
megohms input impedance is required to ensure
accurate voltage readings. The GCP controls output
circuits such as the fuel injectors, electronic governor,
etc., by controlling the ground or the power feed circuit
through transistors or other solid state devices.
The GCP is designed to maintain exhaust emission
levels to government mandated standards while
providing excellent operation and fuel efficiency. The
GCP monitors numerous engine functions via electronic
sensors such as the throttle position (TP) sensor and
the heated oxygen sensor (HO2S).
GCP Inputs (operating conditions read)

Engine Coolant Temperature

Crankshaft Position

Exhaust Oxygen Content

Manifold Absolute Pressure

Battery Voltage

Throttle Position / Electronic Actuator

Fuel Pump Voltage

Intake Air Temperature

Camshaft Position
GCP Outputs (systems controlled)

Fuel control

Electronic Throttle Control

Electric Fuel Pump

Diagnostics - Malfunction Indicator Lamp (check
engine lamp)

Diagnostics - Data Link Connector (DLC)