3-14 ENGINE CONTROL SYSTEM
SPS (Shift Position Sensor)
The SPS is installed on the throttle lever holder and detects the
shift position with the clutch lever operation interlocked.
This sensor is a variable resistor that changes resistance (ohms)
in accordance with the shift position.
The varying resistance value is converted to voltage and input to
the ECM.
Based on the SPS voltage, the ECM calculates and determines
the change of shift position and executes the following controls.
• When the shift is in neutral, fuel injection is controlled to pre-
vent engine speed from exceeding 3 000 r/min.
• After shifting into forward or reverse from neutral, the IAC
valve is controlled to increase intake air for 0.1 second to pre-
vent unstable engine idle or stalling.
ECM MAIN RELAY
The ECM main relay is installed in the electric parts holder.
When energized by turning the ignition switch ON, a circuit is
formed which supplies battery voltage to the ECM, fuel injector,
ignition coil, IAC valve, CMP sensor, high/low pressure fuel
pump, purge valve, OCV (Oil control valve) and VSV (Vacuum
switching valve).
CRANKING SWITCH SIGNAL
The ECM detects the engine being started by the position of
ignition switch key. When the ignition key is turned to ST posi-
tion, a voltage (12 V) signal is input to the ECM.
The ECM in turn controls the actuators for ignition, fuel injection,
IAC, etc. to the starting mode.
With the key is turned to IG position after the engine has been
started, the input voltage becomes approx. 1.4 V.
Shift position sensor
ECM
main relay
+12V
3
2
ECM
1
OFF
ON
ST
1. Ignition switch
2. Neutral switch
3. To starter motor relay
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