Crankshaft Position Sensor: Description and Operation
Fig. 33 Crankshaft Position Sensor:
The Crankshaft Position sensor (L5)
Crankshaft Position Sensor Location:
The crankshaft position sensor (L5) registers the crankshaft position and engine speed. The position sensor is mounted to the crankcase above the starter flange.
The sensor body projects through the crankcase very near to the segments on the flywheel/drive plate. There is no contact between the segments or the position sensor.
Flywheel/drive Plate Segments:
With the engine running, the two segments which are positioned 180° apart pass by the position sensor. Due to induction, an alternating voltage is generated in the position sensor. The peak voltage is approx. 1.5 volts at starting speed. The voltage rises with increasing speed to approx. 3 volts at 1200 rpm.
Postion Sensor Oscilloscope Pattern:
t1 = First Segment
t2 = Second Segment
d = Period for one crankshaft rotation
The crankshaft position is recognized from the voltage signals which are produced. The segment front edge generates a negative voltage signal. The segment rear edge generates a positive voltage signal. Engine speed is determined by measuring the period (d) which is equal to one crankshaft revolution.
The alternating voltage of the position sensor is passed along the control lead (coaxial lead) to terminal 7 at the ignition control module. the lead is a single-core cable and the screening is used as a second lead.
If the control module does not receive a signal from the position sensor, the complete ignition system is inoperative, e.g. an interuption of the sensor coil can cause this.
No TD signal exists if a short to ground is present at the equipment or at the diagnostic connector terminal block terminal TD (X11). to locate the problem, detach the single wire connection at the (X11) connector. Rectify short to ground in the prospective circuit.
The following components have a TD connection: Tachometer,CFI control module,fuel pump relay and compressor cutoff control module.