Crankshaft Position Sensor: Description and Operation

GF07.04-P-6220MAR Component Description For The Crankshaft Hall Sensor
- ENGINE 156.981 in MODEL 230.470 as of Model Year 09 /Modification Year 08 model refinement package

View of engine from rear left







B70 Crankshaft Hall sensor

Location
The Hall sensor is located behind the LH cylinder head at the transmission flange.

Task
The Hall sensor contactlessly detects the position and rpm of the crankshaft over the increment wheel (perforated plate) on the starter

Design
The Hall sensor and its electronics are cast into a plastic housing with a 3-pin plug connection. The clearance to the increment wheel is dictated by the installation position and is 0.3 to 1.3 mm.

Function







1 Increment wheel (perforated plate)
B70 Crankshaft Hall sensor

The Hall sensor scans the perforated plate with 58 stays and the gaps of 2 stays (60-2).
Each 4 mm wide link generates a signal change at the Hall sensor. In the center of the stay, the signal changes from approx. 5 V (high) to about 0 V (low). No signal change takes place at the gap with the 2 missing links. At the second falling (negative) edge following the gap, The ME-SFI control unit (N3/10) detects the top dead center position of cylinder 1.

Only the falling signal edge of the signal is evaluated. For a frequency measurement, the gap between two negative edges must be measured.
The signal from the rising (positive) signal edge is fluctuating and is therefore not used.