Throttle Position Switch

Throttle Position Switch type sensors are very basic and are rarely used on the modern engine. They detect when the throttle is at full throttle or at idle. This particular throttle switch is a two position sensor and has only three pin outs. Another type is a three position sensor making it a four pin out switch, this gives the driver that extra gradual throttle response for better economy. These are both also adjustable, to ensure optimum operation and also good economy.

From zero to fifteen degrees, the ohm reading is at 0.5ohm. At fifteen degrees, the resistance shoots to an overload reading (O.L.). As the angle increases, up to seventyfive degrees resistance stays in overload (O.L.). From seventyfive degrees the resistance is back in range, at 0.5ohm.

Throttle Position Sensor

The type of TPS sensor we use here is called a Linear throttle position sensor or Pontentiometer type sensor. Potentiometer type sensors hold a variable resistor with a slide contact inside of them. As you push in the accelerator and the throttle butterfly moves, the contact changes its position on the variable resistor. As the throttle position changes the output voltage from the sensor changes. As the throttle opens (throttle position angle increases) the resistance is decreased, thus increasing the output voltage from the sensor:


15` - voltage is at 1.4v
30` - 2.1v
45` - 2.6v
60` - 3.1v
75` - 3.6v
90` - 4.7v


Idle puts out a low voltage (the least voltage) and this is how it is recognised. Usually about 0.4 - 100mV.