G643(E) Service Manual
Chapter 5. Engine Management System (EMS)
181
EMS Inspection and Repair
Engine Control Module
[
G643E
]
The 48-pin Small Engine Control Module (SECM)
and sensors provide the computational power,
algorithm logic, sensor inputs and control outputs to
control the system. The SECM receives signals from
the sensors, digitizes these signals, and then,
through algorithms and calibration MAPs, computes
the desired output response to effect control of fuel,
spark and air to the engine. The SECM also
provides a variety of other functions and features.
These include system monitoring and diagnostics to
aid in maintaining efficient system operation and
auxiliary control.
SECM/sensor inputs and control output specifica-
tions are specific to the application, but include a
selection of the following:
Analog Inputs
The 48-pin SECM is equipped with sufficient analog
inputs for the following sensors.
•
Manifold Absolute Pressure (MAP) 1bar MAP, 0 to
5 V
•
Manifold Air Temperature (MAT)
-40°F to 266°F (-40ºC to 130ºC) range, 48 kohm
to 85 ohm sensor range
•
Throttle Position Sensor 1&2 (TPS1 & TPS2) 0 to
5 V
• Foot Pedal Position 1&2 (FPP1 & FPP2) 0 to 5 V
• Coolant Temperature Sensor (CTS)
-40°F to 266°F (-40ºC to 130ºC) range,
48K ohm to 85 ohm sensor range
• Fuel Temperature Sensor (FTS)
-40°F to 266°F (-40ºC to 130ºC) range,
48K ohm to 57 ohm sensor range
• HEGO (3) 0 to 1 V
• Auxiliary Analog Input (2) 0 to 5 V
• Battery Voltage (Vbatt) (1) 8-18 V
With the exception of battery voltage, all inputs are
0-5 Vdc, ground referenced. Resolution should be
0.1% or better. Accuracy should be 2% or better.
Frequency/Position Inputs
• Crankshaft position
Variable reluctance (2-wire, 200 Vpp max) or 0-5
V Hall Effect with calibration selectable pull-up
resistor for open collector sensors Permits speed
resolution of 0.25 rpm and crankshaft position
resolution of 0.5º
• Camshaft position
Variable reluctance (2-wire, 200 Vpp max) or 0-5
V Hall Effect with calibration selectable pull-up
resistor for open collector sensors.
Digital Inputs
• Oil pressure switch
Normally open, internal pull-up resistor provided
to detect external switch to ground
• Transmission oil temperature switch
Normally open, internal pull-up resistor provided
to detect external switch to ground
• Fuel select switch
Three-position switch for bi-fuel applications to
detect gasoline mode, LPG mode, and fuel off
(center switch position)
• Ground speed select switch
Permits selecting two different maximum engine
speeds
• Vswitched
Switched battery voltage
