Throttle Position

This is the reading from the potentiometer at the manifold - it is not a reading from the accelerator pedal

You may see that this reading never reaches 0%, and in some cases does not also reach 100%. There are a few reasons for this:

• The reading is relative. 13% on the potentiometer may be fully 'closed' in terms of throttle. On some vehicles this also represents the idle state (on these vehicles 0% would mean fully closed throttle - no air=engine stall).

• For readings that do not reach 100%, this may also be due to the relative reading of the potentiometer. The ECU map may also contribute to this as on some vehicles the throttle (controlled by the ECU) will close slightly at higher RPM - the VW Fox is one such vehicle that does this over 3000RPM.

• You may see a rarely changing reading for Diesel vehicles. This is due to diesel engines not using a traditional 'throttle', but instead control power varying the amount of fuel entering the engine (unlike petrol engines which starve the engine of air(throttle) to control engine speed/power)