Trouble Shooting Throttle potentiometer and How It Works

The throttle potentiometer is used to determine the opening angle of the throttle valve. The information gained is sent to the control unit and is one of the factors used to calculate the amount of fuel required. It is attached directly to the throttle valve axis.

Function

The throttle potentiometer is an angle sensor with a linear characteristic. It transforms the respective opening angle of the throttle valve into a proportional voltage ratio. When the throttle valve is actuated, a rotor connected to the throttle valve axis moves with its contacts over resistor paths, which transforms the position of the throttle valve into a voltage ratio.

Effects of failure

A faulty throttle potentiometer can become noticeable as follows: 
■ Engine judders and/or stutters 
■ Fuel feed to engine is poor 
■ Poor start-up behaviour 
■ Increased fuel consumption 

Reasons for failure of the throttle potentiometer can be: 
■ Contact fault at the pin connection 
■ Internal short-circuit caused by soiling (humidity, oil) 
■ Mechanical damage

Troubleshooting
The following test steps should be taken into account during troubleshooting: 
■ Check the throttle potentiometer for damage 
■ Check pin connection for correct fit and soiling 
■ Check voltage supply of the control unit (circuit diagram for pin assignment is necessary). Ref. value: approx. 5 V (refer to manufacturer's information).

■ Resistance measurement at the throttle potentiometer (circuit diagram for pin assignment is necessary). Connect the ohmmeter and test the resistance with the throttle valve closed, slowly open the throttle valve, observe changes in the resistance (during measurement an interruption of the loop contact can be established). Test the resistance with the throttle valve fully open (refer to manufacturer's instructions). 

■ Check the cable connections to the control unit for continuity and ground connection (circuit diagram for pin assignment is necessary). Test the individual cables and the component connector for continuity with the control unit connector removed, reference value: approx. 0 ohm. Test each cable for a ground connection against vehicle ground, reference value: approx. 30 MOhm.




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