Camshaft Sensor

Camshaft Sensor

Camshaft sensor
The camshaft sensor is attached to the cylinder head cover.
The camshaft sensor detects the position of the intake camshaft using an increment wheel (camshaft sensor wheel) attached to the camshaft. Should the crankshaft position sensor fail the engine-management system will use the camshaft sensor to calculate engine speed. The camshaft position sensor and the crankshaft position sensor are both needed to control injection (individual injection events for each cylinder at an optimal time relative to the firing point).

Functional description
The camshaft position sensor tells the engine-management system whether cylinder no. 1 is currently on the compression stroke or intake or exhaust stroke.
The camshaft sensor is designed as an contactless Hall effect sensor. The camshaft sensor wheel has 6 different flank spacings. The flank spacings are detected by the hall effect sensor.
The engine control system uses these to calculate: here
- Camshaft speed
- Camshaft speed
- Exact position of the camshaft







For starting the engine, the engine control unit checks the following preconditions:
- Error-free signal from the crankshaft sensor
- both signals must be detected in a specific chronological sequence

This process is referred to as synchronization and is only performed when the engine is started. It is only the synchronization process that enables the engine control unit to activate fuel injection correctly. The engine will not start without synchronization. When voltage is applied, it is detected whether the sensor is above a tooth or above a gap.

Structure and inner electrical connection
The measuring procedure is based on Hall IC. The output signal uses a flank to show Low status and a gap to show High status. The camshaft position sensor employs the same basic operating concept as the crankshaft position sensor. However, the camshaft sensor wheel differs fundamentally. A special mark pattern enables emergency operation in the event of failure of the crankshaft sensor. However, the resolution of the camshaft sensor signal is too imprecise to replace the crankshaft sensor during normal operation.







Signal shape and setpoint values
The engine control unit reads in the sensor signal and then compares that signal against a template in its memory unit. By comparing the sensor signal against this saved template, the precise position of the camshaft or the deviation is identified.







Observe the following setpoint values for the camshaft sensor:

Size Value
Voltage range 6 to 16 Volts
Engine speed range 0 to 4000 rpm
Air gap range 0.4 to 1.9 mm
Maximum output current 20 mA
Temperature range -40 °C to 160 °C

Diagnosis instructions

Failure of the component
The following symptoms may be anticipated in the event of a failure in the camshaft position sensor:
- Fault entry in the engine control unit
- Emergency operation with substitute value

General notes
The diagnosis routine for the camshaft position sensor launches in response to the following conditions:
- DME main relay ON
- Engine running
- Engine is synchronized
- No stalling of the engine detected
- Error-free signal from the crankshaft sensor

We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.