Sensors

Sensors
Note: the term TPS can mean either throttle position sensor or throttle position
switch
Throttle Position Sensor (potentiometer)
Potentiometer type sensors are composed of variable resistors that have a slide contact,
which changes its position as the throttle butterfly moves.
A voltage is supplied to the sensor by the E.C.U. As the throttle position changes, the
output voltage from the sensor changes, this in turn is recognised and a comparison made
by the E.C.U to its memory. These sensors are adjusted by loosening the sensor mounting
screws. (It is critical that you follow the manufacturer’s set-up procedure)
For example:
The idle position is recognised by the lowest voltage reading through the sensor but in
contrast, the maximum power signal is recognised by the highest reading at the full throttle
position of the sensor travel. It is important that both signals are correct

Checking the Throttle Position Sensor

What type of TPS is this?
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Explain its internal operation and why your voltage changes
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Now connect a Power Supply to your sensor and test the voltage output at different throttle
angles.
NOTE: Always use a 5V supply

Throttle angle	Voltage output

 Now plot your findings on a graph





Throttle Position Switch
There is an idle position signal that is used mainly for fuel cut-off control and ignition timing
corrections. The power signal is created at full throttle and is used for increasing fuel
injection volume which in turn increases engine power output. Note there is no switching at
part throttle.

Throttle position switch detects throttle position at idle or full throttle by using switch
contacts that are connected or disconnected as throttle position changes.
This type of switch can have two or three contact positions and is usually checked and
adjusted using a multi-meter.
Adjustment is made by loosening the mounting screws and rotating the switch assembly.
On - Off type throttle position switches can have:
Two position (three pin) or
Three position (four pin).



Note: PSW means power switch (WOT)
IDL means idle circuit
E means earth
Plot your findings on the graph

Explain the internal operation of this sensor and why the resistance changes
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