Indirect Type

This throttle position sensor converts the throttle valve opening angle into voltage signals. It has four terminals: VC, VTA, IDL and E. A constant 5 volts is applied to terminal VC from the engine ECU. As the contact point slides along the resistor with throttle opening, voltage is applied to the VTA terminal. This voltage increases linearly from 0 volts at closed throttle to 5 volts at wide-open throttle.

The engine ECU converts the VTA voltage into one of eight different throttle opening angle signals to inform the ECT ECU of the throttle opening. These signals consist of various combinations of high and low voltages at ECT ECU terminals as shown in the chart below. The shaded areas of the chart represent low voltage (about 0 volts). The white areas represent high voltage (L1, L2, U: about 5 volts; IDL: about 12 volts).

Throttle Valve

Angle Signal Chart

IDL

Shaded area = low

Li

voltage (about 0 v).

L2

Clear area = high

voltage (about 5 v).

Li

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ft 7 15 25 35 50 65 Throttle Valve Angle -

ft 7 15 25 35 50 65 Throttle Valve Angle -

When the throttle valve is completely closed, the contact points for the IDL signal connect the IDL and E terminals, sending an IDL signal to the ECT ECU to inform it that the throttle is fully closed.

As the ECT ECU receives the L1, L2 and D signals, it provides an output voltage from 1 to 8 volts at the TT or ECT terminal of the diagnostic check connector. The voltage signal varies depending on the throttle opening angle and informs the technician whether or not the throttle opening signal is being input properly.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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