Day 3 - Throttle Postion Switch

Throttle Postion Switch detects throttle position at idle or full throttle by using switch contacts that are connected or disconneted as throttle position changes.

Measurements

Place the ohm meter across the E and IDL pins and with the throttle shut:

0-1% : 0.3Ω(earth pin and idle pin are connected), 1-100%: infinity

Place the ohm meter across the E and PSW pins and with the throttle open:

0-75%: infinity, 75-100%: 0.3Ω

Graph:

 

The purpose of a throttle postion switch is to tell the ECU that when is at idle or at wide open.

The ECU is programmed to give more fuel when the car is idling to improve smoothness. Also it is programmed to give more fuel when the car is at WOT(wide open throttle) for more power.

If the throttle position switch is faulty, the ECU may send too much or too little fuel at the wrong time.

What is the difference between a throttle postion sensor and a throttle position switch?

A throttle position sensor can measure the full sweep of throttle opening from idle to wide open throttle(WOT). However, a throttle position switch  can have only closed or wide open and nothing in between.