764 Throttle Position Switches

The ECM needs to know the position that the throttle valve is in at any given time, in order that it knows when the throttle is closed and the idle control is required to operate. The throttle position sensor also gives a very good indication of engine load and also the fully open position of the throttle butterfly valve (plate). The throttle position sensor is normally positioned on the throttle butterfly spindle at the opposite end to the throttle lever.

Fig. 7.21 Oscillscope voltage pattern for an analogue MAF
Fig. 7.22 Testing a throttle position sensor (switch)

Figure 7.22 shows a throttle position sensor being backprobed in order to obtain a scope pattern of the voltage signal.

With the time base of the oscilloscope set to a suitable value, the ignition is switched on. The scope screen should then be observed while the accelerator

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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