How the throttle potentiometer works
Throttle potentiometer
Here you will find useful basic information and important tips relating to the throttle valve potentiometer in vehicles.
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.
Important safety note
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.
TABLE OF CONTENTS
HOW THE THROTTLE POTENTIOMETER WORKS: FUNCTIONAL PRINCIPLE
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.
Throttle valve potentiometer
THROTTLE POTENTIOMETER FAULTY: SYMPTOMS
A defective throttle valve potentiometer can manifest itself as follows:
- Engine jolts and/or splutters
- Engine accelerates poorly
- Poor starting behaviour
- Increased fuel consumption
CAUSES OF A FAULTY THROTTLE POTENTIOMETER: CAUSE OF FAILURE
Causes of throttle valve potentiometer failure can be:
- Contact fault at the plug connection
- Internal short circuits caused by contamination (humidity, oil)
- Mechanical damage
CHECKING THE THROTTLE POTENTIOMETER: TROUBLESHOOTING
The following test steps should be considered during troubleshooting:
Throttle valve potentiometer – example OK
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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