Throttle Position Sensor (TPS)

The two types of TPS are the Switching Type, and the Potentiometer Type. The Switching Type has a switch at either peak of the throttles turning circle. As the contact connects with either of these points, it will switch either the WOT (wide open throttle) or Idle circuits. Anywhere in between it will continue normal driving patterns. The Switching Type TPS is quite an early model of TPS, only allowing the ECU to adjust ignition timing under WOT and to activate injector cut-off at idle.

The more modern and also more common style of TPS, the Potentiometer type, has a contact connected to the throttle butterfly, and a set resistor. The contact moves as the butterfly is opened, and is moved across the resistor. The "Rule of thumb" specifications, if run on a 5v reference, are 0.45-0.5v at idle, and approx. 4.5v at WOT. Below is a simple diagram of the inner functions of a potentiometer-type TPS.

 In order to bench test a TPS, we must wire up a 5v supply and earth to two of the pinouts, and connect a multimeter to the output pin. Before we do this, we must ofcourse find the pinout diagram for the TPS. This i found by google searching the part number.

To test, I set my multimeter to DC Volts scale, and open the throttle with my hand. My findings were as follows:
Throttle angle        Voltage output
0°                           0.396v
25°                         1.451v
50°                         1.68v
75°                         3.9v
85°                         4.1v
90°                         4.28v
Below is a graph explaining these findings