Throttle Position Switch

Throttle Position Switch ( TPS)

What does throttle position switch do?

The 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 multimeter.

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)

Testing the throttle position switch

The TPS signal is very important to ensure smooth and economic engine running and the TPS is made to be adjusted to ensure optimum operation.

The condition of the contacts inside the switch is the first test, and should be checked for high resistance in both the idle and full throttle position.

Place the ohm meter across the E and IDL pins and with the throttle shut, Check for continuity.

Place the ohm meter across the E and PSW pins and check for continuity when the throttle is wide open.

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.

When the car is on idle the switch is normally closed and when the throttle butterfly turn "on" the switch then slowly transists to PWC after 20 degrees.