Camshaft position sensor function
Here you will find useful basic information and important tips relating to the camshaft sensor in vehicles.
Important safety information
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 use by suitably qualified personnel only.
The task of the camshaft sensor is to work with the crankshaft sensor to define the exact position of the crankshaft drive. Through the combination of both sensor signals, the engine control unit knows when the first cylinder is in the top dead point.
This information is needed for three purposes:
The camshaft sensor works according to the Hall principle. It scans a ring gear on the camshaft. The rotation of the ring gear changes the Hall voltage of the Hall IC in the sensor head. This change in voltage is transmitted to the control unit and evaluated there in order to establish the required data.
A faulty camshaft sensor can cause the following symptoms:
Reasons for failure of the camshaft sensor can be:
Check the connection line from the control unit to the sensor using the ohmmeter. Remove the connector from the control unit and remove the sensor, check the individual cables for continuity. A circuit diagram is required for the pin assignment. Reference value: approx. 0 Ohm.
Check the connection lines for short circuit to frame. Measurement between sensor plug and vehicle ground, control unit plug removed. Reference value: >30 MOhm.
Check the supply voltage from the control unit to the sensor. Insert the control unit plug, switch the ignition on. Reference value: approx. 5 V (note manufacturer's specifications).
Check the signal voltage. Connect the measuring cable from the oscilloscope and start the engine. A square wave signal must be displayed on the oscilloscope.
Make sure that the distance to the encoder wheel is correct and that the seal fit is correct.