Check and replace throttle valve potentiometer: Function and fault diagnosis

The throttle valve potentiometer informs the engine control unit about the opening angle of the throttle valve. The signal from this sensor is required to calculate the injection quantity, for example. This page explains the design and function of the throttle valve potentiometer. We will also show you which symptoms could indicate a fault in the sensor and how it can be checked in the workshop with simple means.

The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for suitably qualified personnel only.

How the throttle potentiometer works

The throttle valve potentiometer determines the opening angle of the throttle valve. This information is then forwarded to the control unit and used as a parameter for calculating the necessary fuel quantity. It is mounted directly on the throttle valve shaft.

The throttle valve potentiometer is an angle transmitter with a linear characteristic curve. It converts the respective throttle valve opening angle into a proportional voltage ratio. When the throttle valve is actuated, a rotor connected to the throttle valve shaft slides over resistance tracks with its sliding contacts, which converts the throttle valve position into a voltage ratio.

Checking the throttle potentiometer

The following test steps should be considered during troubleshooting:

Check the throttle valve potentiometer

Check the throttle valve potentiometer for damage

Check the plug connection

Check the plug connection to ensure it is fitted correctly and for any contamination

Measure the resistance

Measure the resistance at the throttle valve potentiometer ( circuit diagram required for pin assignment). Connect the ohmmeter and check the resistance with the throttle valve closed; slowly open the throttle valve and monitor the change in the resistance (an interruption to the sliding contact can be identified during the measurement). Check the resistance with the throttle valve fully open (observe the manufacturer's specifications).

Check the cable connections

Check the cable connections to the control unit for continuity and a short circuit to frame (circuit diagram required for pin assignment). Check the continuity of the individual cables with removed control unit plug and component plug; reference value approx. 0 ohms. Also check each cable against vehicle ground for a short circuit to frame; reference value approx. >30 MOhm.

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