Exhaust Camshaft Sensor

Exhaust Camshaft Sensor

Exhaust camshaft sensor
The exhaust camshaft sensor is attached to the cylinder head cover.
The exhaust camshaft sensor detects the position of the exhaust camshaft with the help of an increment wheel (camshaft sensor wheel) attached to the camshaft. The exhaust camshaft sensor is required for the feedback signal to adjust the exhaust camshaft (VANOS).

Functional description
To perform the adjustment, the variable camshaft timing control requires a feedback signal on the current position of the camshaft. Camshaft sensors on the intake and exhaust side record the position of the camshafts. The exhaust camshaft sensor is designed as an inductive 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







A controlled VANOS unit is fitted at both intake and exhaust camshafts. A VANOS solenoid valve activates the VANOS unit. The required positions of the intake and exhaust camshafts are calculated from the engine speed and the load signal (depending on the intake air temperature and engine temperature). The DME control unit activates the VANOS unit accordingly. The control of the intake and exhaust camshaft is variable within their maximum adjustment range.
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 exhaust camshaft sensor operates on the same principle as the crankshaft 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
Maximum operating current Less than 15 A
Engine speed range 0 to 4000 rpm
Air gap range 0.4 to 2.0 mm
Maximum output current 20 mA
Temperature range -40 °C to 160 °C

Diagnosis instructions

Failure of the component:

If the exhaust camshaft sensor fails, the following behavior is to be expected:
- Fault entry in the engine control unit
- Emergency operation with substitute value

General notes
The diagnosis for the exhaust camshaft sensor starts under the following preconditions:
- DME main relay ON
- Engine running
- Engine is synchronized
- No stalling of the engine detected
- Error-free signal from the crankshaft sensor

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