Troubleshooting Camshaft sensor - Automotive Electronics Works

Camshaft sensor

General points
In coordination with the crankshaft sensor, camshaft sensors have the task of exactly defining the first cylinder. This information is required for three purposes:
1. for initial injection in the case of sequential injection,
2. for the control signal for the solenoid in the case of the unit injector system and
3. for cylinder-selective knock control.

Function
The camshaft sensor works according to the Hall principle. It scans a gear rim located on the camshaft. Due to the rotation of the gear rim, the Hall voltage of the Hall-IC in the sensor head changes. This change in voltage is sent to the control unit and evaluated there in order to establish the required data.

Effects of failure

A faulty camshaft sensor can become noticeable as follows: 
■ Engine warning light comes on 
■ A fault code is stored 
■ Control unit works in limp-home programme 

Reasons for failure of the camshaft sensor can be: 
■ Mechanical damage 
■ Break in the sensor wheel 
■ Internal short-circuits 
■ Interruption in the connection to the control unit

Troubleshooting

■ Check the sensor for damage 
■ Read out the fault code 
■Check electrical connections of the sensor cables, the connector and the sensor for correct connection, breaks and corrosion 
1. Check the connection cable from the control unit to the sensor using the ohmmeter. Remove the connectors from the control unit and the sensor, check the individual cables for throughput. Circuit diagram for pin assignment is necessary. Ref. value: approx. 0 ohm.
 2. Test connection cables for ground connection. Measurement between sensor connector and vehicle ground, control unit connector is removed. Ref. value: >30 MOhm. 
3. Test the supply voltage from the control unit to the sensor. Insert the control unit connectors, switch on the ignition. Ref. value: approx. 5 V (refer to manufacturer's information). 4. Testing the signal voltage. Connect the oscilloscope measuring cable and start the engine. The oscilloscope display must show a rectangular signal

Installation note Make sure of the correct distance to the sensor wheel and the seal is seated correctly.



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